Amazing - a retention package and we're all doing ATPLs. No surprise - for everyone who gets a bonus there seems to be one whose been shafted and prompted to leave - me included and I thought I had a glittering career ahead of me.
Anyway, isn't the ATPL(H) requirement for 350 hrs multi-crew experience? I think the 1500 is for FW. I believe you can count all time logged as P1 or captain with a QSP in other seat, but not dual time. The details are on a certificate you need to complete which is on the TGDA website.
Remember, as my good lady tells me watch the Torque on the way up and the droop on the way down.