We have always insisted that spare equipment is available for breakdowns and PM. When this has been explained to the powers that be there has been little or no argument.
Consider the cost if an anaesthetic monitor failed and a list was cancelled because there isn't a spare? That usually focusses the minds of the general managers with their waiting list initiatives. I have not found a single anaethetist/surgeon complain about buying spare equipment.
On one occasion, I discovered an anaethetist wheeling into theatre the spare anaesthetic monitor to reassure themselves of the gas measurements.
A simple analogy: If the consultant's car will not start in the morning and there is a list they need to do they would probably call for a taxi. The excuse of "my car would not start" would not be acceptable, but probably would be believed.
There is of course the question of the ratio of equipment/spares to consider, I suggest this is based on risk assessment for each individual department and undertaken by the theatre manager.
All of this supports good contingency planning and provides assurances to the users of service continuity. (not to mention fewer patients cancelled )