Buying back shares is only one dimensional, as they would not ever sell them back on the open market

http://www.ptsc.com/news/press_releases/20060424.asp

Repurchased shares will be placed in our treasury as a resource available for possible future use," Pohl explained.

I am of the opinion that repurchased shares will eventually find their way back into the float, one way or another... hopefully at a much higher price..