Yes you can add... Just add the second vCenter, and create a new provider VDC.
The real fun is around catalogs and templates.
Here is the quick - how it works.
I will assume catalog items are on VC-01 for purpose of this little info block. When a item is needed on VC-02 vcloud will make a shadow over to the other vcenter. Now it does this via 2 methods.
1. ExportOVF (HORRIBLE)... but sometimes just required. [vcloud does it, but it is very slow and really puts a strain on the system]
2. Direct datastore -> datastore CopyFile. This is the best way - however it is really picky. You cannot have chain length > 1 on a catalog item if you want to use this. Also you need to make sure all hosts (on both vcenters) can access any datastore with catalog items. [However the trick - you CANNOT add the catalog datastores in vcloud to the new provider vdc; or the system will really causes on odd issues.
I know this info is not 100% complete; but hopefully can get you thinking about what you need more details on.