Considering we have already have cheap things to detect nuclear proliferation, such as seismic detectors that have proven effective w/ North Korea and how expensive a neutrino detection system would be to build, I don't see any marginal benefit to humanity there. Considering the fact that you would need to build a beamline for any transmission of a neutrino message and a 5 ton detector to receive it (unlikely to be reduced since it's so hard to stop neutrinos) I'll stick with my > 50 year timeline for neutrino message passing being used in any practical sense. Maybe they could put it in a nuclear sub, but the design process would take 50 years, thanks to similar incentives built into the military industrial complex.
Seismic can only detect an explosion. Neutrino can detect the construction. If the threat comes from someone who has reactors and already knows how to make bombs, seismic is too late.
A 5 ton detector isn’t particularly implausible in a whole range of scenarios.