Landlord owns the phone room typically. Anything in it related to telco is owned by the local Telco wiring from street and any equipment. Wiring within the buildings are owned by the landlord and tenants depending on arrangements they have.
We used to do this all the time The telco tests to the demarc I.E Phone room and from there its your or tenants responsibility to troubleshoot. It worked very well for us.
We used the Zxyxel I think 24 port VDSL dslam units and the CPE that worked with it.
Sometimes in huge apt buildings the landloard works out an agreement that the telco or cable company owns and maintains the inside wiring as well so its less of a headache to the landlord and tennant.--
ComTrain Certified Tower Climber.
Wireless and IT consultant.
Proficient in Mikrotik