Just my tongue in cheek take on this...
Suppose I have some guys working on my house, so purely a domestic situation..do I, as the instructing principal, have to provide toilet facilities?
Why would I not? Ok, so some random guys take a dump maybe once a day in my loo...is it really a problem? I have 2 loos, so not a problem really.
However...if the guys here are plumbers, they have to disconnect the loo, what then? I cannot let them use my loo, so do I have to provide them with some temporary facility by hiring a porta-loo firm?
Near to my house is a very well respected company who often do work in the estate. They have offices 500m away. Even so, they always bring in a portable loo for any job that is over a week, such as a complete kitchen and bathroom refit. They charge plenty, but it suits them and the customer. My near neighbour had his kitchen and 2 bathrooms remodelled recently. he went on holiday for a fortnight. The contractors brough it a potable loo on day one, even though their office was so close.Simple, cost effective, sensible for all concerned. maybe just a premium service, but clearly they though it worthwhile.
I had to have a contractor in recently, and i provided him with toilet facilities too. ..I gave him the key to my sister's holiday flat which is next door!