I've worked for two BA subs.
One had no pension scheme, the other was in the BA pension scheme.
They had varying travel perks and degrees of management independence.
One payroll was done by BA Pay Services, the other (after BA PS cocked up the MDs salary twice), wasn't.
When a facility shared between BA PLC and a sub was closed recently, there were major differences in redundancy packages, depending on which side of the line the employee worked, although both wore the same uniform.
Working for a wholly owned subsidiary does not mean you work for BA PLC.
I now work for an IT company, largely on the BA account. Essentially, BA pay my wages. Does this mean BA employ me?