There is no statistic for "in office" listening.
In diary Nielsen markets, we had "home", "work", "in vehicle" and "other" as listening locations in that market, but now with PPM we just have "home" and "away". The PPM has no way of knowing if a person is at work or just out of their home.
And much, if not most, work listening is not in offices. It is at the loading dock, the shipping department, the stock room, the construction site, the auto repair shop and similar locations.