For what it's worth, there is still an official talking clock phone number one can call to get the time. I don't know how much latency POTS and cell phone service have, but it's something.
I just tested it against https://time.is on my cell phone (using wifi calling because network strength is abysmal where I live).
I don't have a precise measurement but it was imperceptibly close, within 100ms probably. Certainly close enough to set a clock for non critical purposes.
https://nrc.canada.ca/en/certifications-evaluations-standard...