The A318 will, eventually, run on PW6000 and a ( I belive) a de-rated CFM56.
To answer I/O's question; Druk Air of Bhutan had an Airbus demo recently as they are looking to replace the 146s. Airbus took the A320 or A319 (memory failure again) there, even if it was bigger than required, since it had the best power-to-weight ration. The A318 did not offer sufficient power even if it was the right size aircraft. Once again referring to my fading memory, I belive Boeing declined to demo the 737NG in Bhutan. Druk Air was amongst the buyers of the now cancelled RJX.