As far as I know the only users of TETRA outside of Airwave customers are airports, TfL, and the Prison Service.I was thinking of non blue light users of Airwave like systems, such as the utilities.
There are a lot of antenna sites that stupid people might attack, or could be targeted to cause trouble for the user. A lot of businesses and the utilities depend on all sorts of RF and microwave systems that have nothing to do with mobile phones.
You’re right about utilities, they use a mix of ptp broadband links and low bandwidth telemetry.
A long time ago I was an old-fashioned analogue trunked-radio SME and knew MPT1327 and MPT1343 almost by heart. Kind of got left behind, though.