The email states that the cabin crew will be Titan Airways but an Easyjet rep will be onboard. Allocated seating is to be abandoned with refunds where necessary, but Speedy Boarding will be in place for those who have paid for upfront or extra legroom seats.
As stated there will be operations by Titan at LGW for peak months made up of a single 757. This is described as an extra line of flying...
The aircraft will be fully manned by Titan and also a 'supernumary' member of staff from easyJet cabin crew. This will be to ensure a consistent on board experience for the customer. I would suggest there will be little difference to flying on usual easyJet service except you get to fly on 757...
EI-BUD