Well, I will add my two cents worth...it is my understanding, from discussions with my legal friends that LEGALLY (in Canada, not sure about the US), they cannot confiscate your equipment, nor can they ask or force you to erase images that you have already taken...they can definitely ask you to leave and they may record your visit. In addition, if you broke a window, or a lock, forced a door or window, then you can be charged not only with trespassing, but you could also be charged with Break and Enter offences, wilful damage to private property, public mischief etc. If you are charged with B & E, then they can impound your car if you used it to get to the place - they will probably have to give it back, but they can impound it, not sure for how long, but I suspect they can keep it until a judgement is rendered or you plead guilty to the B&E charge...
There do not have to be any signs posted, e.g., No Trespassing, for you to be charged with trespassing, after all you are technically on private property and were not invited in. This may be moot if there are no fences and the gates or doors are open, but don't push it. Also, if you run into problems and are injured, then the property owner is not liable for damages to you or your equipment.
My advice, get permission and if you do, carry it with you when you go to visit. This is about all I know for the Canadian scene, not only that, these "rules" may have changed in recent years, so check the current laws/rules/regulations.
Cheers,
WesternGuy