Actually, it's a K20 engine... which is from the Civic Type R. But, the US's Atom (Built by Brammo in Oregon) will have different engine options, and the only engine offered in the same spec as the UK is the top end supercharged K20. The US Atoms will be built with US spec engines, both Honda and GM's.
Here's a list of costs:
Brammo Ecotec 2.2 $35,000 145 HP/ 155 Ft./lbs.
Brammo Ecotec 2.4 $38,000 171 HP/ 163 Ft./lbs.
Brammo Ecotec 2.0 Supercharged $40,000 171 HP/ 163 Ft./lbs.
Honda K20 (Estimated) $40,250 USDM K20z3 200-225HP
Honda K20 Supercharged $45,750 (K20z3) 290-300HP