I’m a software engineer with colleagues who work with various localization and short range communication. This is totally technologically feasible. All the “what if it’s not sure” cases just default to the higher limit. It won’t be sufficient for self-driving cars to know how fast to drive, but it will prevent the vast majority of excessive speeding.
The what-ifs are just people either flailing around to not have their speeding curtailed or people who assume half-assed apps from companies that don’t have any reason to care if they’re right are the state of the art. They always come up with absurd reasons why they need to speed or why implementation is impossible whenever any road safety improvement is proposed. It’s a boring and pathological response.