Yes, they can bring their own poles and fish in the canals around the Fort. Just know that it is catch and release.
You can not fish in the lake unless you are on a boat.
How much is the excursion?
It is $270 for 2 hours & $455 for 4 hours. If you are a DVC member, have an annual pass, or Disney VISA card there is a 15% discount. They provide the boat, guide, fishing tackle, and bait. They have a cooler with drinks. It is catch and release.