Great thread. Yes, this is, unfortunately, a question I ask myself every activation.
If you ask permission (good boy), you risk an ignorant CYA bureaucrat-type shutting you down, just because that's easy. Been there. But there are other times when we should realize there exists a legitimate concern. Such as: (1). Hundreds of feet of wire and coax in a crowded park, near where lots of people are; (2). Operating that might go after hours when the park is supposed to be closed ... even if you're only in a parking area; (3) Using a structure like a fire tower, as if it's yours alone to use ... ouch this one hurts the most.
Generally, I look for an inconspicuous location, and don't ask permission.
GL and 73, David K2WPM