Blue Square and VC are cages rather than skins on the same network. The network is Tribeca Tables.
A cage is a site that offers its own banking facilities. A skin is a site that uses someone else's cage for banking facilities.
The Grand Prix Qualifiers are only available on Blue Square - and Blue Square also runs daily freezeouts with added prize money at 8.30pm that are not available on the rest of the network - spam over

Hope this clears it up for you.