Or may be bluetooth beacons? Like these: https://www.amazon.com/programmable-Battery-Bluetooth-eddystone-Technology/dp/B078N2B7RD/ref=psdc_172504_t1_B07Z1FR6GY
Those are cheap.
KPN is a legit lora provider, see their lora-website. Yes, they too want you to get into contact. Which is fine, you can probably get them involved in a PoC, if the businesscase is sound. Lora is mainly for tracking small items that move around in ‘outside’ areas. Each Lora-tracker is about 10 euro, might be more, or less, but just to let you know that it is not 1 cent per tracker.
If the yard is fenched and has only one or two gates, then an option is cameras and licenseplate recognition.
And another option: if the company does have the trucks gps location available in a company-application then use that to detect if they are on- or off-premise.
One client I worked with had GPS trackers in their vehicles which reported back to a central server via a mobile phone data connection that I could query via a REST API from my Mendix application. We used these to plot locations on a map, but in your case, this could be to check that the vehicle is either in or out of the geofence. I’m afraid I don’t know which provider they used, but it seems a fairly standard technology.
LoRa is low-powered and useful for occasional small packets of data. One client I worked with used this for reporting back temperatures from static locations. I’m not sure this is really suitable for you but could work.
Personally, I’d look at the GPS tracker that uses a mobile phone provider's data network and has an API exposed for querying locations of those tracked devices.
Hope this helps.