Found the official entry list. Yes, the two 370Z's are being fielded by RJN of the UK. No engine specs but they list their displacement as 3.8L, so they may either be running the GT-R block or a custom crank shaft.
The 1 GT-R entry is by JRM, also out of the UK. Displacement is listed as 3.8L as well so this looks like a traditional turbo set up.
24H Dubai - Provisional Entry list 24H DUBAI 2012 : endurance racing for touring cars, GT cars and 24H Specials by 24H Series