I have a T440p and using it with two external monitors connected through VGA and Mini-Displayport (one vertical, the other horizontal, both 1920*1080) and not using the laptop display itself. I also don’t use a dock and my monitors are connected to laptop directly. I'm planning to buy an ultra dock.
After searching a bit just saw lots of issues with using both VGA and HDMI ports on dock to use two monitors simultaneously. Since nearly all of these threads were older than a year or so, I wanted to check if what I'm trying to do is possible or still there is a problem with that.
I use ubuntu 12.04 LTS, but if upgrading to 14.04 LTS will solve the problem I can do that.
Best Answer
The issue appears to be lack of MST support in the Linux kernel. Upgrading to Ubuntu 15.04 with kernel 3.19 fixed the issue for me, but only after I installed the proprietary nvidia drivers.