Yes you of course are right Diesel it does obviously depend on where you are based as to the value of BALPA to your own cause.
As regards Scope in theory its a good idea , unfortunately its open to abuse/persuasion (whatever you care to call it). MAN and BHX were good examples of this where BALPA just gave away those bases and work to City Express.
OK its part of the BA umbrella but its not on the master seniority list and BALPA don't appear to be pushing it either.
So scope in these cases has led to a B class salary, standby LGW. All the company has to say is oh dear we can't afford full pensions and salaries at LGW and down will come the portcullis at Fortress Heathrow. We aleady have the capped salary scales so the rest unfortunately will follow.
Scope is a tool to protect LHR and BALPA, as BALPA's main contributors in BA are LHR based (market forces and all that). However once all the outstations have become B class citizens with B scale pay then the attention will turn to the next minority at LHR.