Unable to get 2560x1600 resolution from Dell U3011 connected to M4600 laptop with NVidia

My setup:
- Dell U3011 30'' IPS monitor
- Dell M4600 Laptop with NVidia Quadro 1000M 
- Simple E-Port replicator model PR03X
- OS: Ubuntu 12.10, kernel 3.5.0-21, 64-bit (I know it is not supported officially, RHEL is, so I guess there should be a way of getting it work)
- Drivers: NVidia proprietary drivers 304.48 (also tried with 304.60)
- X.org version: 1.13 

According to the specs the monitor should be capable of doing 2560x1600 through DVI-D or DisplayPort. 

The problem is: I can't get it to work with DisplayPort even if directly plugged to the laptop. 
The Nvidia driver seem to detect DP properly, although it doesn't detect the monitor. It only detects the laptop LCD display. If I go to Nvidia Settings, there is no eternal monitor listed.

What I tried and what did not work:

• turning off optimus in Bios
• connecting the monitor first, then rebooting,
• first booting then connecting the monitor
• pressing Fn+F8 several times
• going to Nvidia Settings and pressing "Detect Displays" - the monitor goes out of sleep mode for a while but enters sleep mode in a few seconds later, nvidia doesn't detect it
• installing different versions of nvidia drivers (the newest I tried was 304.60
• uninstalling bumblebee totally (optimus is off in bios anyway)
• using nouveau open-source drivers (they seem not to work at all, even for the laptop display)
• removing xorg.conf entirely

X.org logs:

[    25.551] (II) NVIDIA(0): Creating default Display subsection in Screen section
<------>"Default Screen" for depth/fbbpp 24/32
[    25.551] (==) NVIDIA(0): Depth 24, (==) framebuffer bpp 32
[    25.551] (==) NVIDIA(0): RGB weight 888
[    25.551] (==) NVIDIA(0): Default visual is TrueColor
[    25.551] (==) NVIDIA(0): Using gamma correction (1.0, 1.0, 1.0)
[    25.551] (**) NVIDIA(0): Enabling 2D acceleration
[    25.561] (II) NVIDIA(GPU-0): Display (LGD (DFP-0)) does not support NVIDIA 3D Vision
[    25.561] (II) NVIDIA(GPU-0):     stereo.
[    25.562] (II) NVIDIA(0): NVIDIA GPU Quadro 1000M (GF108GL) at PCI:1:0:0 (GPU-0)
[    25.562] (--) NVIDIA(0): Memory: 2097152 kBytes
[    25.562] (--) NVIDIA(0): VideoBIOS: 70.08.54.00.01
[    25.562] (II) NVIDIA(0): Detected PCI Express Link width: 16X
[    25.562] (--) NVIDIA(0): Interlaced video modes are supported on this GPU
[    25.605] (--) NVIDIA(0): Valid display device(s) on Quadro 1000M at PCI:1:0:0
[    25.605] (--) NVIDIA(0):     CRT-0
[    25.605] (--) NVIDIA(0):     LGD (DFP-0) (connected)
[    25.605] (--) NVIDIA(0):     DFP-1
[    25.605] (--) NVIDIA(0):     DFP-2
[    25.605] (--) NVIDIA(0):     DFP-3
[    25.606] (--) NVIDIA(0):     DFP-4
[    25.606] (--) NVIDIA(0):     DFP-5
[    25.606] (--) NVIDIA(0):     DFP-6
[    25.606] (--) NVIDIA(0):     DFP-7
[    25.606] (--) NVIDIA(0): CRT-0: 400.0 MHz maximum pixel clock
[    25.606] (--) NVIDIA(0): LGD (DFP-0): 330.0 MHz maximum pixel clock
[    25.606] (--) NVIDIA(0): LGD (DFP-0): Internal Dual Link LVDS
[    25.606] (--) NVIDIA(0): DFP-1: 165.0 MHz maximum pixel clock
[    25.606] (--) NVIDIA(0): DFP-1: Internal Single Link TMDS
[    25.606] (--) NVIDIA(0): DFP-2: 165.0 MHz maximum pixel clock
[    25.606] (--) NVIDIA(0): DFP-2: Internal Single Link TMDS
[    25.606] (--) NVIDIA(0): DFP-3: 165.0 MHz maximum pixel clock
[    25.606] (--) NVIDIA(0): DFP-3: Internal Single Link TMDS
[    25.606] (--) NVIDIA(0): DFP-4: 480.0 MHz maximum pixel clock
[    25.606] (--) NVIDIA(0): DFP-4: Internal DisplayPort
[    25.606] (--) NVIDIA(0): DFP-5: 480.0 MHz maximum pixel clock
[    25.606] (--) NVIDIA(0): DFP-5: Internal DisplayPort
[    25.606] (--) NVIDIA(0): DFP-6: 480.0 MHz maximum pixel clock
[    25.606] (--) NVIDIA(0): DFP-6: Internal DisplayPort
[    25.606] (--) NVIDIA(0): DFP-7: 480.0 MHz maximum pixel clock
[    25.606] (--) NVIDIA(0): DFP-7: Internal DisplayPort
[    25.606] (**) NVIDIA(0): Using HorizSync/VertRefresh ranges from the EDID for display
[    25.606] (**) NVIDIA(0):     device LGD (DFP-0) (Using EDID frequencies has been
[    25.606] (**) NVIDIA(0):     enabled on all display devices.)
[    25.607] (==) NVIDIA(0):.
[    25.607] (==) NVIDIA(0): No modes were requested; the default mode "nvidia-auto-select"
[    25.607] (==) NVIDIA(0):     will be used as the requested mode.
[    25.607] (==) NVIDIA(0):.
[    25.607] (II) NVIDIA(0): Validated MetaModes:
[    25.607] (II) NVIDIA(0):     "DFP-0:nvidia-auto-select"


What works "partially":

• Connecting the monitor using the VGA cable. Then I'm able to get the 2048x1240 resolution, but the image quality is poor, it is blurred. Not a solution really. In this setting the NVidia driver does detect the monitor as U3011 properly.
• Connecting the monitor using DVI-D (dual-link) cable through the dock station. In this setting the NVidia driver does detect the monitor as U3011 properly, TwinView works fine.
  However, I get only 1600x1200 resolution as the highest option (even not the 1920x1200 which is supposed to work with single-link DVI).
  Might be that the docking station doesn't support dual link DVI?
  The connector on the back of it is dual-link for sure, but maybe there is no dual-link connection between the laptop and the dock?
  Unfortunately the laptop doesn't have a DVI-D connector, only HDMI, VGA and DP, so I can't try direct connection.
  Or maybe the driver is misdetecting dual-link connection as a single-link and in fact it could be possible to force it to use dual-link pixel clock?