It was a matter of time, CityJet don't have a replacement for the RJ planned and the global fleet is rapidly shrinking. Airfleets suggests that Jota are the only other RJ operator in Europe, this must make support and maintenance more challenging. As pointed out BACF can operate the route quite well from within the IAG stable, they could even operate in EI colours if desired. If EI do want to get back to LCY the options are limited if they don't use the E170/190. The A220, E170, E190, Q400 and ATR are the only 'modern' aircraft which can use LCY. Unless IAG order the A220 in large numbers it is unlikely in EI colours and it is limited in the number that can be on the ground at any one time at LCY, for now. Would someone like LOT operate the Q400 on a wet-lease? Which brings us back to the ATR, most likely by Stobart, but could be anyone.

Depends how good the yield is, I guess?