Interesting one this. I'm not really a conspiracy person by default but the cell tower angle is something I've actually looked into a bit after the 2011 Christchurch quake, where there were similar claims.
The thing is, towers going offline right before a quake could have a totally mundane explanation - foreshock damage to infrastructure, power fluctuations, or just the fact that people are retrospectively connecting two unrelated events. Our brains are wired to find patterns even when there aren't any.
That said, there IS documented research into electromagnetic anomalies preceding seismic events. The LAIC theory (lithosphere-atmosphere-ionosphere coupling) has actual peer reviewed papers behind it. So if someone somewhere was monitoring that and knew what was coming, well. That opens a different kind of question doesn't it.
Does anyone have actual timestamps or locations for the towers that supposedly went dark? Without that its all a bit vague. Would be genuinely interesting to cross reference with the USGS foreshock data if the specifics are out there.