Surely, the whole ethos of EZY mitigates against the C Series replacing the 319. Just imagine the cost of type ratings for 1/2 the pilots - & then being unable to use them on the 320. Although, I suppose, you could keep them busy on both types in order to keep the Ratings current & the operation flexible.Would they do this ? Then there would be new recruits who would have to get both ratings, or only able to fly 1/2 the fleet.
You would , presumably, repeat the whole procedure for maintenance & cabin crew etc.
On the other hand, EZY have not ordered any 319 NEOS to replace any that are getting a bit "long in the tooth". Does this give any credence to the rumour ?