RBN is a way for people to put music on rock band. most of the times people hire an authoring group to make the charts etc. for them.
some mainstream bands also do this, but some people also got their own songs on it
if you are on xbox you can get all RBN content if you're account is from one of the countries that allows for XNA content. (from the top of my head: US, England, Spain, France, Canada, Germany and maybe some more) if you're on PS3, 5 songs will be ported over from Xbox to ps3 once a week. on ps3 it doesn't matter what country you are in.
songs can be pulled, but this happens very rarely once they hit the in-game store.
if you download them from XBL dashboard however, then there is a slightly bigger chance they might get pulled.
and no, paradise city was not on there
