The story does point out that they were doing a "full day of work", then going home even if it was still morning. So there doesn't seem to have been any person

The story does point out that they were doing a "full day of work", then going home even if it was still morning. So there doesn't seem to have been any personal benefit from the time dilation - the crew still put in 8 hours of work per person per day. Sending a guy across the tunnel to deliver some tool still costs the same amount of his workday, but it'd be instant for the people on the outside, which would save a bit of time. On the other hand dealing with the weirdness and scheduling around it might well eat up any time gained. Now if they'd convinced the head office about the weirdness, I suppose they could have dispatched another dozen crews and gotten 80 hours of work done each day - at least in the tunnel.