The book describes Strahd having two methods of gaining information.

Strahd is able to scry on the characters. This is his best method for knowing about the party's adventures as you play.

Strahd has many spies who report to him each dawn and dusk. Among these are many of the Vistani. The Vistani are the only people who can enter and leave Barovia at will. They are probably Strahd's best source of information about things that occur outside of Barovia.

Given this mundane method of gaining the information you want him to have, there is little reason to metagame the crap out of this.

I'd say no

The way I read this:

No spell — not even wish — allows one to escape from Strahd’s domain. Astral projection, teleport, plane shift, and similar spells cast for the purpose of leaving Barovia simply fail, as do effects that banish a creature to another plane of existence. These restrictions apply to magic items and artifacts that have properties that transport or banish creatures to other planes.

it isn't like an Anti-Magic field or something where the spells themselves don't get cast, it's their effect that is disallowed, so whether the spell was cast outside of Barovia or not isn't relevant.

I also read "for the purpose of leaving Barovia" to include being summoned out of it, because the person already outside trying to "summon" the person inside still have purpose of someone leaving Barovia, which seems within the scope of what the quoted text is trying to prevent.

That's my reading of it, anyway...