You're both very welcome!

As FLY is now live in some outstations, flights leaving those outstations will be in FLY and only FLY. For that reason, even though Heathrow (and to a lesser extent Gatwick) haven't transitioned, to receive these flights and deal with transit passengers etc. they need to have access to FLY and know how to use it. I believe there was focus placed on getting transfer staff training complete before the switchover began. I imagine that's why you saw FLY in the arrivals lounge MPH1980. I believe there's also an iPad app for staff available to help deal with the problems that will arise from having two different systems live and some flights in one system and some in the other.