BR
There are still two diffrent pay scales (at the time of posting) though this is still being negotiated, any new employees will be on the MYT payscale, T+C etc... this is due to MYT being the host AOC for the merger.
Base list have already been published in the company and although there are still some changes that are likely to happen by the time the recruitment and training has been started all bases will have been merged together and both companies will be acting as one.
As for applying i would advise applying to the one in the advert as mentioned in a previous post.