Entering into our main client base here, so I'll say how we do it. By the way in the vast majority of multi occupancies the landlord is never on site as they are some large multinational investment agency, pension fund or bank - it falls to the managing agent to meet the RRO responsibilities.
If the landlord's agent has staff on site (such as contract security or a buliding manager) then it's easy to draw up an evac strategy with staff acting as a roll call coordinator (RCC) and ticking occupiers off on an evac checklist as tenant's wardens report in (as well as reading the fire panel). The RCC the acts as a single point of contact for the FRS giving building wide information.
All tenants receive copies of the procedure.
Unstaffed (by the landlord or agent or their contracted site staff) buildings are more problematic. In some premises one of the tenants (usually the major tenant or if it's a Govt Agency they often volunteer) formally agrees to act as the RCC and takes the overall responsibility.
Understandably some tenants may not wish to take this additional burden and thus the procedure includes a warden assembly point near the entrance so at least when the FRS arrive they can rapidly get the idea of the building's status without chasing around to find multiple dispersed wardens as they should all be in one place.
This is all backed up by sending all occupiers copies of the procedure, accepting feedback, carrying out monitored drills for compliance & sending letters out reminding tenants of their obligations if they are not playing ball.
Ultimately after all this if some tenants still refuse to play then it's up to the FRS as the landlord has demonstrated due diligence in taking all reasonable steps to co-operate or co-ordinate.
