Yes, the Halo Mega Bloks set is different because they're intended to be for the Halo series. They have a less "child-like" feel to them because of how action-oriented the Halo series is, making them much different than the ordinary Mega Blok sets.
It is assumed that Mega Blocks will release Halo: Reach sets, and they are highly anticipated.
I think about the closest you'll get is the Covenant Combat Unit that has some Covenant Elite soldiers in it.
No. The mega bloks tracks are more narrow. Mega block thomas trains are designed so that the wheels are about as wide as the 2 by 6 block they are attached to. The LEGO duplo thomas train wheels are set so the wheels sit outside the footprint of the block they are attached to. This makes their tracks much wider than the mega blok tracks. I haven't tried this yet, but you could probably swap the wheels. If you have some duplo trains you won't be using, you could probably take a mega blok train off its wheels and put in on a duplo set of wheels.
barbie, tuffling.
Blok M is at Jakarta
Peter Blok's birth name is Blok, Peter Stephanus.
Marnie Blok's birth name is Marina Ann Catharina Blok.
Alexander Blok died in 1921.
Alexander Blok was born in 1880.
Anton Blok was born in 1935.
Vlaams Blok ended in 2004.