Having detailed experience and knowledge of the situation in Sri Lanka, I can tell you that it would be completely out of character for the LTTE to hook up with any Muslim group. It would also be out of character for AQ to hook up with the LTTE against the Tamil Muslims as well. The chance of any cooperation between the two is nil.
A certain mind of murderer begins to take a pride in his method, his style, his mechanics. The killing is a cherry to that pride in workmanship. An idolatrous pride, it grows and is greedy for one's soul, one's psyche, everything in one's life.
That kindred of a murderer, no mere religious impulse nor social trainings will find him bound to one side or the other.