J636,
Yes BE selling cheap flights ex BHD, good luck if you can get it as a one way, without booking a return, they tend to load the return flight with a higher price.
They have a complicated pricing system. I've often heard people saying I only had to pay £15 for my flight out to X from BHD, but no mention of the return flight. I may drive a strong price perception.
Flybe getting close to BA of late, that might explain BE entering onto LCY routes, and putting the airport as a significant base for future expansion, including flying on some of BA's own routes. Alas BA responded.
If paying a fee to participate in Avios scheme is cheaper and easier to manage than their own scheme, well them it makes perfect sense, if Avios can profit from bringing BE into the portfolio, then on a commercial basis it is right. I wouldn't see that as an indication that BE and BA are getting closer. BA also have only got very small stake now in BE....