There are several levels to your question: Practicality, UL Rating, Acceptance.
- Will the power-limited wires (low voltage wires) be routed through spaces in the box reserved for power-unlimited wiring (utility power or battery power)?
- Will the power-unlimited wiring be routed through spaces reserved for power-limited wiring?
- Will the hole, conduit connector or bushing, or wiring be placed in the space reserved for the batteries?
- Will the added wiring prevent proper servicing and access to the circuit boards?
If the answer is yes to any of these questions, then, from a standpoint of what is practical, drilling holes for wires isn't a good idea.
Questions about the actual UL rating for the box can be best answered by the technical support people at the power supply's manufacturer.
Even if it is practical to drill holes, even if technical support says that the UL rating won't be violated, it may not be acceptable to the Authority Having Jurisdiction to drill holes.
Read: Just Who Is the Authority Having Jurisdiction (AHJ)?
to get an understanding about who actually makes decisions about the fire alarm system.
Remember, if it's the fire marshal or the electrical inspector that says you can't drill holes, that person is a representative of the government. It isn't a non-profit publishing house like the National Fire Protection Association (NFPA) that makes laws, it isn't a private company like UL that makes laws, it's the government that makes the laws that we have to live by. Being a representative of the government, if the fire marshal or electrical inspector doesn't accept drilled holes, that's the final authority.