Tire pressure monitor sensors...

[Bouchedag84]

Hey guys,
So I bought my x5 and a few months after the tire pressure sensor went off and sure enough I had a low tire. Got that fixed. Anyways, several months later I got my rims/tires changed for winter by a tire shop where I purchased my tires and supplied my own after market rims. I never considered the tire pressure monitor system. I don't know where it is connected or how t works even. Would I be safe to assume that the tire shop would've reinstalled the tpms into my winter tire/rim setup? How do I check this and ensure they didn't just remove or disconnect them?