Simultaneous contacts for P&D tankers is allowed iaw ATP-56(B) (para 106g):
"
Individual Clearance to Contact. Normally, the tanker is only able to safely monitor one receiver at a time. Consequently, receivers will be cleared (verbally and/or by light signals) to make contact one at a time. Where the tanker is able to monitor both receivers, simultaneous contacts may be approved."
Contacts during tanker attitude changes are captured under Safety Procedures, specifically para 404e:
"(5) Prohibited Contacts/Disconnects. Contacts/disconnects are not to be permitted during tanker attitude changes."
Although there should probably be a "Caution" attached to that - I'll get me pen...
Steady turns, as Beagle suggests, are fair game, except for some CONVEX activities (same para as above):
"(6) Contacts/Disconnects – CONVEX. Some nations require that, during receiver CONVEX, tankers will order all contacts/disconnects in straight and level flight unless the receiver supervisory pilot requests otherwise for training purposes."
The whole book is available here:
RAF - Air to Air Refuelling - ATP-56(B)
Not heard about a Boom being lost either - but I take Beag's point about it being naiive to assume simultaneous contacts are safe, I'm not convinced the previous ban on doing so was only due to lack of visibility of receivers from the tanker.
And anyone suggesting just turning off the lights needs a smacked bottom.
Oh, and the video is very sexy - I wonder when we'll see the KC767 equivalent (i.e. fully functional Boom and Pods)?