TAM is not yet a full *A member. I have recently flown the IAD-GIG seasonal route on a TAM ticket, but in E+, not C. I just make sure that UA has my MP No. when checking in, and the miles are credited, both EQM and RDM. According to the info in the chart on .bomb, P would earn 125%.
http://www.united.com/page/article/0,6722,52289,00.html
but note the asterisk and fine print:
As of July 1, 2008, all travel on TAM credited to the Mileage Plus program accrues actual miles, with no minimum.