The company made it clear that FFers reaching a new milestone would be given those threashold bonuses. So for example, if you had 1.5 million miler status with US, it just converted over to Lifetime Gold status with AA. You already had Million Miler status with US (nothing new was achieved). However, if you had 900,000 MM from US and 100,000 MM from AA, once they were combined, you become a MMer for the first time and receive the 35K bonus along with the status. Moreover, if you had over a 2 million miles with US, you get the Lifetime Platinum status plus the 4 SWU's because that was a new achievement since US had nothing above Lifetime Silver. But once again, the 35K bonus miles are part of the 1MMer achievement. Which was already accommplished.

BTW, December 2011 has zero impact regarding cross-over US million miles. Only actual miles flown on US metal (and its merged predecessors) count towards AA Million Miler status. Before or after December 2011.