Well my understanding that the percentages accepted are quite small, but since transfer admission depends heavily on 1L grades, if you do well you can end up getting in somewhere much higher up than where your LSAT/U-grad scores put you initially. One friend of mine just transferred from GW (having low-160s LSAT, maybe 3.5 u-grad GPA) to Columbia-- based on his 1L performance and a really interesting resume (fluent in several languages, many leadership activities). Another got waitlisted at U Michigan from Brooklyn law.
So it's certainly possible. But from what I hear, to have a good shot you want to be near the top 10% of your class.
i also go to GW. did you friend place top 10%? at first i had figured that this would be necessary to do in order to transfer, just as others looking to transfer have to do. however, when i got to school this year, i heard from others that lower T14's will take people from GW who place only in the top 25-30%. i wonder if this is true. though i'm sure that columbia is a much different story than, say, georgetown.
but another question. with a 3.5/low 160's LSAT, did you friend by chance start in the PT program at GW?