Switch PI on/off via LTE HAT (& Power Management HAT) via Webhook or SMS?

Hi, in the next days my sixfab 4G/LTE Cellular Modem Kit will arrive. It is supposed to be installed in my old-timer van with the purpose of GPS-Tracking, remote ODB-Monitoring, wifi hotspot, music streaming etc. Is it possible to have the LTE HAT running in low-power mode and have it switch on the PI when certain trigger arrive (e.g. an SMS)?

I am currently looking into the Mausberry Car Supply Switch or the Sixfab Power Management & UPS HAT.

I wonder, if keeping the LTE HAT in a state, where it consumes the least possible amount of energy and just listens to a trigger, would be possible. An arriving trigger leads to powering up the PI enabling remote access to it, as well as continuous GPS tracking. Appreciate any ideas. Thank you - Johannes

bump - any thoughts? Is it so trivial, that I just don’t get it or is it just not possible? any answer is appreciated very much.