But, in my personal situation, our contracts are generally for longer terms, so I guess it is a fixed office - and we have a fixed HQ too. The issue is that y

But, in my personal situation, our contracts are generally for longer terms, so I guess it is a fixed office - and we have a fixed HQ too. The issue is that you have no control over the location of these changing "fixed" offices, so your employer is free to assign you to a customer halfway across the country. Sounds exactly like the kind of situation this ruling is supposed to protect against.