I think Jets are a bit of a double edged sword. The extra range would be useful, the issue with Large regional jets are the seat costs. The props offer lower seat costs and lower capacity than the A320/737s on the shirt UK hops. RJs just offer less capacity, but at a higher seat cost. As flyBe found, operating large RJs in a price sensitive market is very difficult.
The question is do EI have a large enough volume of routes with time sensitive, high yielding traffic which are byond the range of an ATR, but don't have the passenger volume to operate an A319 profitably.