I can understand Anonymous chose to fight ISIS in their own way. The world should oppose these murderers, but a cooperation between them and the government? Not gonna happen.
It doesn't even need to be cooperative. USG could changetip from it's CIA twitter account for the lulz, though possibly it would never be withdrawn. Its unlikely that they understand the full nature of Anonymous, but the idea is interesting and weird.
Anonymous can't be bought, but maybe there is a way the USG can pay without subverting or creating the appearance of subverting?