OK, this is not a done deal (yet). Here's the latest from Tanguay:
http://www.csnne.com/author/gary-tanguay/
"UPDATE: It is also my belief that Grant Hill will sign with Boston after meeting face-to-face with Doc Rivers by the end of the week. Glen Davis could be gone to San Antonio, as they are prepared to offer their mid-level slot, which it is my understanding that Boston will not match. Davis is a restricted free-agent and any offer he receives can be matched by the Celtics within 7 days."
So the Spurs will not get Davis cheap. The Celtics want him but only at a decent price and will match if the offer is low. But if San Antonio offers close to the MLE, Baby is gone. (That's overpaying though. He's a nice player to have but he's not worth that much.)
The Grant Hill to Boston report seems solid though.