Yes it is, they will map jump points and start making jumps from the initial system, from what I've understood. I've never gotten beyond encountering them though, as my games haven't gone into multi-system empires, and their initial incursions into Sol results in them being flattened in missile swarms from 20 FACs.
I've got some invaders that are running around surveying the survey points and stuff. Is this normal behavior for invaders? I have a stable wormhole two jumps from my homeworld and I'm worried.