I do not think I have explained myself correctly. The LCY flights are a BA Mainline service with a BA mainline product and as such must be operated by a BA mainline base as per our AOC, nothing to do with union clauses, something a lot of crew in BA seem oblivious too.
There are exceptions to the rule however such was when Hire ins or required for technical reasons or if a wet lease is signed with an operator. However if it is to be operated by another set of crew such as cityflyer then it has to be on cityflyer metal and operated as a franchise service!!! As is my understanding of the whole operation. Now there is nothing to stop BA setting up an LCY base on cheaper T&Cs but then that would have its own additional costs and perhaps not worth it just for two daily flights!
I do not know how the AML thing worked with the 777s in LGW but I do know that the flights were operated as "British Airways by AML" or something to that effect even though they were BA metal with BA pilots, either way there was a clear and distinct differentiation made as to who was working on those flights with the customer!