From the hardware side, extremely precise. Most discussions assume the sweet spot for ISAC is in "Frequency Range 3" (7 - 24 GHz, decent penetration and range, very good resolution), and in that range you can pin down objects with millimeter precision (both position and velocity). So, not only can you detect people walking down the street, you can detect them breathing when they stand perfectly still.

This, of course, requires 6G base stations to be spaced pretty tightly (hundreds of meters apart) and to feature sophisticated phased array antennas. But both can be assumed in cities (they're planning to completely replace WIFI with 6G, so every current WIFI access point will become a 6G micro cell). Walking humans can be detected much easier, but radar SNR is funny, that only gives you 4x-6x the detection range.

Software (signals processing) for all that will be... a lot of difficult work. Object separation/tracking, multipath reflections, clutter suppression, ect.

Although this is a preprint it shares some discussion and ideas on how to mitigate potential privacy challenges of ISAC.

https://eprint.iacr.org/2026/1069

I suspect while not individually, it will provide another data point that can be collaborated.

One should never underestimate the power of combining data sets.