When I removed all updatesites and added just http://download.jboss.org/jbosstools/mars/development/updates/ (should have just mars cr1), install and then ran check for update my updatesites contained neon references.

See https://www.dropbox.com/s/xo040iyhiw9zhsw/Screenshot%202015-09-24%2009.41.01.png?dl=0

I'm not sure if I even needed to do the check for updates, but those are the steps I did.

note: I install everything and uncheck the "check all updatesites"