They don't use magitech, necessarily. Player Engineers doesn't need to, and nothing of Engineer skills directly says it uses magic (last I checked, at least; it wasn't like I sat down and went through the skills to be sure).

They just use tools. What those tools are powered by varies with the engineer that designed them. A player can role-play as a magic-distrusting (see: Charr) Engineer with no issues regarding their tech supposedly being magitech.

That isn't to say that Tyrians don't usually use magitech; they do (e.g. Asura...anything, really) for many tasks while using base technology for other tasks. Fishermen don't use magic fishing rods (though lures may be), for example.

As a character profession, whether or not it is magitech is completely up to the player if they feel like they want their character to use base tech or magitech. Most Tyrian tech is magitech in some way, but several groups don't use magic in their tech. Notably, Harathi centaurs specialize in non-magical tech (while Tamini are fighters and Modniir are casters), along with most of the Iron Legion technology not involving magic in any way but being used to combat it or complement it on a battlefield. A Charr Tank providing support fire is not magitech.