Here are the rules.
This is from my experience with dealing with arsonists. There will somehow someway be some sort of notification to the FD, no matter what it is but in order to do arson you need admin permission and I assume you would need a reason as to why you would like to set fires.
There was an arsonist by the name of "Firebat" months ago and they would set fires to businesses and this gave roleplay for the LSPD and LSFD. There is no limit and no off limits it's 100 percent based off the administrator's decision as to whether you can set something on fire or not. My suggestion, get approval first before you do any roleplay in regards to arson, explain the reasoning but remember that you cannot control the outcome of whether LSFD is notified or not, 99 percent of the time they will be notified.