Anyone can have an Ethernet leased line , it’s normally business as they can be expensive compared to FTTP , if the car dealership either side of you can order FTTP as well as Ethernet leased lines , then ordering FTTP is an address based system, so presumably their address has FTTP availability on the appropriate checker sites , and presumably you think your business address as it’s a neighbouring address should have FTTP availability as well , I assume it’s a business that your enquiry is about given this statement, ‘seems a strange coincidence that the properties between the commercial businesses that use a private line have no fibre and there is no plans to connect them to fibre’ or are you residential customer, if a residential customer presumably your residential address is contained within a business area , perhaps you can clarify what you are , a business or residential customer.
Business addresses can be difficult to match , if a car dealership is next to you it’s likely it’s not known with a ‘normal’ format address like , No.1 Coronation Street , but something like Billy’s Bargain Bangers Coronation Street , so how do you know they have native FTTP ?
Use this checker site for your address and the neighbour address that you state can get FTTP
https://www.broadbandchecker.btwholesale.com/#/ADSL
you can search using a postal address or UPRN , post the entire return
