Pretty sure he was just throwing beer on the audience for the most part at those shows, he certainly wasn't blind drunk like at previous ones. However he plays a character during FBHT shows so if that thing about smiling and winking is true it wouldn't surprise me whether he was really drinking or not, he was acting as the Rev at the time!
I don't recall that Billie has promised anything about what he will and won't drink anyway though? Not everyone who goes through rehab pledges to be teetotal for life afterwards. He's been pictured with a beer in his hand on a few occasions since rehab and nothing terrible has happened. At the end of the day it's his business.
A Foxboro show after one of the Green Day ones (in London perhaps ) would be very welcome if they still have it in them to pull that off. Or one on a free night during the tour. Of course during the 21st CB tour they had Prima Donna (and therefore Kevin Preston) on tour with them as support and that made it a lot more feasible, but I think it could still be done.