You need to convert or render your m2t file. Vimeo recommends H.264 which is also known as mp4 or AVC. In Vegas you can use either the Mainconcept or Sony AVC render option and follow the settings below.
Here is Vimeo's recommendations directly off their help page.
Can you recommend some encoding settings for HD?
Yes. Your quota for the week is 500MB, so itÃÔ a good idea to compress your video down from phenomenally high quality to just amazingly high quality. We recommend using the H.264 codec at size 1280×720, bit rate 3000-5000 kbits/sec (optimized for ÅÅownload?, key frame every 30 frames (frame reordering on), using whatever frame rate you shot in. For sound, use AAC at 128kbps in stereo.