Insofar as it’s convenient and fulfils its imperatives for it to remain δ-coextensive with its host culture, the Transcend defers to the Empire in terms of expansion, and the Empire is as modestly philoprogenitive (and likewise pro-immigration) as one might expect of a healthy culture.
It does have very strict standards for being allowed to join (after all, wouldn’t you be very picky about who you allowed into your brain?), but not all that much stricter than those for “people we want around the Empire in the first place”.