Piglet's reply really says it all. The next question concerns where the teneants are. Are they all in one building? Or is this supported living as in they live in their own homes and the support services visit them individually? If they are all together in one premise / building who owns / operates the building as a facility offering supported living? Are the tenants in the care of Social Services? the NHS? or somebody else?
The answers to these questions will indicate who owes duties of care to whom.
Supported Living has manyu attractions regarding independence etc. It also keeps the operators out of the Care Homes legislation applicable in Scotland.
As for the evacuation of persons in wheelchairs, this is going to depend on all of the answers above and when the property concerned was actually built. at the risk of driving you crazy, was it built / occupied as a place where persons with support needs were anticipated to be living? Support needs as in physical assistance for their escape? An easy answer to question would be the requirements of the Fire (Scotland) Act 2005 and the Fire Safety (Scotland) Regulations 2006 need to be satisfied. But only to the extetn required by the Act and the Regs and that takes us round in a loop to the first series of questions.