Joe Two,
You are, indeed, correct. There are DEC positions within OS. Infact the recruitment has been open to a limited number of BA line pilots who wish to be 'seconded' to OS for a minimum of 4 years on OS T's & C's.
As far as joining OS as a DEC from an FO's position in mainline, it's a non starter. BA have already stated that a command course within OS will not be accepted when the secondee comes back to mainline and they will have to wait and re-do the command course as appropriate. Somewhat questionable to me as the command qualifications/course should, surely, be adequate for OS and Mainline unless the management are accepting below par training for their new fledgling?
Even if the common seniority list were to be accepted, any DEC positions who wish to transfer to the mainline from OS would lose their commands as they take up their natural seniority position within the company.
AFAIK there will be no grandfather rights.
It's all in the melting pot at the moment but, oddly enough, there doesn't seem to be a queue at the door to OS from Mainline.
As to the T's & C's, BA is still billed as an 'aspirational' carrier. Which means that they, at the moment, have no lack of applicants wishing to join. If the T's & C's at any major carrier be it BA or Virgin are slashed then there is no incentive to move carrier. The management will know this and therefore reduce any incentives they may have to entice people to remain with their company. As the top starts to slip the degradation WILL roll downhill. Why would any current management maintain any half decent T's & C's when they know that the pilot workforce has nowhere else to go?