If a company wants me to be on-call or do any kind of mobile work, they can give me a phone. I let this slide at one job because it was a unicorn where I actually loved the job, but from then I've been able to get corporate phones and it's been key.
... but if you're SRE oncall, you'll probably have that phone on you (or at least within hearing distance) at all times when you're on shift. I'd assumed the relevant issue was having a tracking device on your person your employer can access, not whether the employer was footing the bill for the tracking device they encourage you to have on your person.
Again anecdotally: most employees I know just set it up on their personal device. It's more convenient than carrying two devices around when one knows one'll be carrying a smartphone anyway.
You don't have precious, irretrievable data on that device anyway, because it's a phone (as in, "There's nothing Google's gonna do to your phone that wouldn't happen to it if you dropped it in a toilet, probably don't keep the only copy of your baby's first words on something that fragile").
So, a separate device would save your from that part, at least.