T&R Pilots, unlike external hires, effectively get to choose between Long Haul SO (777 / 787) or A320 FO. The Company will offer them the first course that comes up (usually A320) and they were allowed to decline and wait for their preference. If however they turned down the second offer they were to be removed from the Jet Seniority list. Whilst not expressly written anywhere, they cannot sit in the Regionals and wait for the LHS of a Jet, nor would they meet the Requirements for a Command anyway.
Unfortunately, it's recently come to light that a few have been abusing the system with the help of their managers who were "incorrectly not applying the 2 offers rule". Along with "being unable to release certain Pilots".
Any Pilot sitting on T&R who has no intention of taking a Job should be removed. All they're doing is blocking their Junior Colleagues who actually do want it.