My boost incognito has signal in the same places my girlfriend's LG Lotus (with Sprint proper) does. We have the same PRL software, and are prone to roaming through the same spots, so that qualifier is false. Also, Sprint's claims that their Nascar and NFL applications are exclusive to post-paid are false, too. Only SprintTV is exclusive.
Then again, my phone DID get water damage a few months ago, so that might've probably 'rooted' my phone, or whatever it is that feature phones do to cancel carrier restrictions.