It seems like the backlash against the diesels has been watered down, a quick look at some regulations for 2011 says they are allowed incorporated into new engine regs for the classes (v10 and v12 are now banned):
I'm devastated to be honest it's outrageous.
How can it be fair to pitch a 2.0 single turbo petrol against a 3.7 twin turbo diesel?
And to make things even worse the weight advantage that a 2.0 petrol would have is even taken away, both cars are forced to have the same weight!
Alas, diesels probably will continue to dominate le mans...