I tried the Canon 16-35mm f2.8L II lens today with various degrees of success. For starters, this lens is not a good lens for IR. It has a large hot spot in the centre of the frame, even when there is no stray light hitting the lens. Almost all Canon USM lenses allow you to focus beyond infinity, and that's what is needed to achieve infinity focus for IR. Most pictures turned out to be in focus when the lens was set beyond infinity to the maximum allowed. This is good for pictures that focus to infinity, but not too good if the focus distance is closer. Some experiment is required. This is the reason I like using manual focus lenses, especially the Pentax-M 20mm f4, for IR. When set to infinity, everything is pin sharp from a couple meters away at small apertures.
The cemetery - Canon 20D IR & Pentax-M 20mm f4. Click for larger.
Geese - Canon 20D IR & Pentax-M 20mm f4.