The XL1s is more than capable of working with IR. However, the nasty bit is you'll need an IR or 'Night Vision' adapter lens to have that capability. NV adapters get really expensive. There's only one outfit I know of that makes a rig dedicated to fit the XL series cameras and that's Astro-Physics. They make solid gear and you may find a used 9350XL on E-bay for a grand or two, but beware at that price there's sure to be damage. New or nearly new you're looking at $5900 and up just for the lens. There's two adaptors that go with it that houses the functioning part and they cost $1200+ a piece. Now you can get by with a cheap IR illuminator for when it's too dark even for the NV unit.
Here's a link for what you're looking for:
If you're looking to buy a good used one message me as I might sell my unit if the price is right.