My job is going through a merger, and the main office will be moved ~100 km. Most of us will continue to work at the old offices, but for those that have to change locale, the union has negotiated the following compensation, which I think is fair, but still not enough for me:
If your commute has increased with more than 40 km, you will get enough increased pay to cover the cost of public transport ($1000-6000/year). If your commute has increased with more than 50 km you will also get to work up to 2 hours a day on the train/bus. You have to actually work those hours, but it still makes a difference to only have to be at the office for 5-6 hours/day. In addition, more people will be allowed to work from home.
I'll continue at the current office, but will have a lot of meetings at the main office. Those travels will be covered as ordinary work travels, meaning I can count all hours as work, get all travel costs refunded, and get a per diem.