For the most part, you can scout, but there are exceptions (one sight, for example, is a national guard training site, so access is limited at certain times). If you go to the IDNR website, there's a section with links to individual public land sites. There will be sight specific rules there. There should also be contact info, and, if in doubt, call. Here's the link:
http://www.dnr.illinois.gov/hunting/...actSheets.aspx
I don't know about cameras, except to say that public land in Illinois tends to get crowded, and I would think the risk of theft would be high.