You can work from home but only to answer us when we contact you. You must answer our contact and must report to the location if requested. If you can do something cheaper (for us the company) and faster (for us the company) then that is the only time you may perform a work duty at home.
It's EU law that if you have to be standby to pick up the phone and go on location at a moment's notice, those are working hours and need to be paid in full. Most companies are pretty careful to not put it anywhere in the contracts or house rules that you have to be on stand-by, but just verbally keep pushing for it. If they keep pushing, push back with asking for the written rules.
"I cannot answer the company contact after hours because for every call I get after hours that isn't a company contact, following an order from work to monitor those on the chance of a company contact itself represents 'working from home' which the company forbids. I cannot violate the previously stated company policy."