sleemanj:Peppery:
From what I understand speaking to multiple property managers in my family, he is not legally allowed to do this,
Landlord is permitted on the grounds, within reason (quiet enjoyment restrictions), but not in the premises (buildings you rent) without appropriate notice.
It sounds like these are just dummy cameras, I'd probably thank the landlord for taking initiative to deter crime, and remind him, and the property manager, that you'd like him to let you know when he is going to be performing maintenance on the property in future, leave it at that.
Agree with the above and if the neighbours have a problem with them, that is between them and the landlord and not you.