I worked on that boat for just over 2 years...
Basically the boat is dropped back on a quick release so that the outdrive was in the water (stored raised using trailer tilt), engine started and warmed up. When RIB crew ready quick release is pulled by deck crew, RIB slides down ramp and when mother ship is clear can be used as normal. Launch speed for mother ship was around 4 knts.
Recovery meant coming up to stern ramp, powering the bow up onto the ramp and a quick link is passed by the deck crew to the RIB crew (needs min of 2 on RIB), which is attached to a winch. As the tension is taken up on the winch cable the RIB helm has to cut the engine and raise the leg before itc comes over the back of the ramp. RIB keel has a stainless reinforcing strip along it's length.
They ve got a (?)5.9m Delta with 180bhp inboard diesel driving a Mercruiser leg. There is also refuelling facilities on board.