Not AFAIK. Sony Vegas makes them for any audio file you use and all they are are small cache type files that make it quicker to import and modify [in vegas] that audio file. https://www.custcenter.com/app/answers/detail/a_id/567 http://forums.creativecow.net/archivethread/24/229393 I am unsure why these would be in your beta.
Maybe they did some quick trimming of audio clips in Vegas/Similar program just for a quick fix, left the .sfk files behind. Could have been done on a different workstation that didn't hold their audio editing software. Doesn't seem all that unreasonable to assume.