The Machine Spirit is (mostly) an abstraction. The AdMech as a whole is a collection of tech support geeks whose documentation and manfiles were converted to hymns 10,000 years ago. Very few members actually have any significant understanding of what they're doing anymore. They just know that if they speak the Holy Words of System Reset and then poke the button with a circle on it, the machine spirit dies and resurrects anew.

So, mostly, no, AI has been well and truly eradicated in 40k and most of what is referred to as "Machine Spirit" is just semi-basic technology being crabby like it already does in the modern day. When a modern programmer says his system is "thinking" or is "upset" he doesn't mean it literally - AdMech just forgot that language wasn't literal.

That said, there are a few suspiciously intelligent and well-informed Machine Spirits in a few places. A couple of them can outright hold a conversation.

There is, actually. They are one of three things:

AI, VI, Warp Spirits.

Plenty of machines have AIs that are either hiding, hibernating, or degraded. There are also plenty of VI programs that are just very complex and sometimes will function in ways their users don't understand.

The rest... Well, belief matters when your species is made up of latent psychics. The best way to get a helpful machine spirit is to treat it with respect, so a decent number of machines that had VIs become something more with time. Not only will it empower the spirit, it will prevent it from falling to Chaos...

In theory.

In my mind that’s what they were, though as a kid I had clippy in mind instead of Siri