GT3
Without being facetious, re the coffee shop "rumour" - have you tried asking EGSS yourself, or getting your Union Reps or Tech Com to enquire on your behalf? I would have thought that, as this is an important issue for EGLL, somebody there would be taking the EFPS development/implementation team to task on this, and many other items.
I know it's the norm to be kept in the dark within NATS, but it might be prudent to remember the old adage "don't ask - don't get". Otherwise, the ol' rumour mill starts grinding away.
The actual asking of the question will hopefully focus the attention of said EFPS team, who may just realise that you're not just going to blindly accept all they say, and if there are concerns about the kit, then they need to be addressed and resolved prior to installation - not after.