Here is some basic info about X200 UltraBase: portable dock for the X200-series ThinkPads (X200, X200s, X200 Tablet) providing extra ports (notably DisplayPort), Ultrabay Slim slot and an additional battery slot.
Positives: eases up portability of laptop, provides digital video output, provides option for optical drive, allows effective use of second battery
Negatives: reduces cooling capabilities a bit (mainly HDD)
DisplayPort support in Linux
Kernel support for DisplayPort in intel graphic chips using KMS (Kernel Mode Setting) was added by Keith Packard in version 2.6.31. On the userspace side driver version 2.7 or newer is required to use KMS. In order to activate it you need to pass modeset=1 parameter to i915 driver either at boot time or in your initramfs.
When passing module parameter at boot time you need to precede it's name by module name followed by a dot so in this case you would need to add i915.modeset=1 to your boot command line.
To pass module parameter in initramfs simply add it to your modprobe configuration and update your initramfs with update-initramfs command.