BTW, does anyone know the tax treatment of share buybacks?

In the US, there is no tax impact for the buyer of the shares at the time of the purchase--tax impact comes when those shares are sold at a later date.  So for the company that buys back shares, it is not a taxable event.

For the person who sells those shares, he of course has a taxable event, and will recognize long or short term capital gain, or capital loss,,,,,,depending on how long he has held the shares, and how the shares have performed in that period.