I'm sure someone already responded but I'll give it a shot.
Company is buying back shares. the intelligent investor will KNOW that the PPS will increase BEFORE the buy back begins and will want to get in now (todays pps rise). Once the buy back begins, the buying pressure from the company will drive the price even higher as there is less shares on the market (kinda like when the fed reduces the amount of money on the market ie drives the price of the dollar up). Decreasing the supply of shares will increase the interest which will increase the demand which will increase the price of existing shares (suppy n demand economics).
Couple that with the fundamentals of the company, principles involved in the company, vision of the company and you get a pretty attractive find for those with enough internal fortitude to take a chance, believe in their DD and put their money where their mouth is.