I doubt we would, but I still say we could.
Paul, people who need access to maintain equipment are dealt with quite specifically:
17.—(1) Where necessary in order to safeguard the safety of relevant persons the responsible person must ensure that the premises and any facilities, equipment and devices provided in respect of the premises under this Order or, subject to paragraph (6), under any other enactment, including any enactment repealed or revoked by this Order, are subject to a suitable system of maintenance and are maintained in an efficient state, in efficient working order and in good repair.
(2) Where the premises form part of a building, the responsible person may make arrangements with the occupier of any other premises forming part of the building for the purpose of ensuring that the requirements of paragraph (1) are met.
(3) Paragraph (2) applies even if the other premises are not premises to which this Order applies.
(4) The occupier of the other premises must co-operate with the responsible person for the purposes of paragraph (2).
It is a toothless comment, as there is no offence directly linked to this requirement. However, if a fire alarm system failed to perform its function, actually creating an offence, and that could be traced back to someone who wouldn't let the engineer in to maintain the equipment, then that tenant could possibly be guilty of the offence. (In a similar way as discussed recently regarding sprinkler systems, and the recent thread regarding a hotel)