So basically, you win VIP when upgrading from colony to starbase.
This is VP cummulative if you built several starbases?
Each time you upgrade a colony to a starbase, you get 1 VP. You don't gain (or lose) a VP when you steal a starbase (or have one stolen from you). This isn't stated explicitly, but I think it's suggested by the table on page 18 of the rules. Similarly, you don't earn a VP when you gain control of an abandoned starbase (via an Encounter card).
It would seem that you do gain 1 VP if you steal a colony and then later upgrade it to a starbase...