They don't actually work anywhere else than on BT, for now at least.
However, it'd be interesting if, on the continent chosen for an invasion, it does not trigger until some advy actually does collect the portal stones and opens a portal himself.
Would be quite amusing if humans brought the invaders to their own lands.
Well it would be an amusing way to settle which island is the next one to get smoked, right? Why, whichever one is foolish enough to allow someone to make use of some portal stones. A little tinkering to make sure they start showing up more often (and that they actually do something sinister when activated), and your pot is on to boil...
