The competition authorities are forcing BA to provide UK connections to non-partner airlines at certain rates (I've no idea what those are) to promote completion at LHR, so there is no pressing need for non one world airlines to encourage BE to LHR. The failed VS experiment with Little Red suggests to me that there isn't much money in flying mainline equipment on UK domestic routes, even when the slots were "free". Its even more telling that flyBe or Aer Lingus didn't apply for the slots after VS announced their intentions to withdraw from UK flying.
Remember around that time EI had 4 aircraft dedicated to the operation - it found better use for all 4 from Dublin and flyBe were looking for homes for the E195 fleet, which have since been based at CWL and DSA.