It's possible that a buddy and other surface support could have cycled fresh cylinders down to him. I usually carry a spare tank, and it's not unusual for me to have a backup reg as well. Depending on how bureaucratic the agency doing the work, they may have had to have a standby diver on the surface as well. Once rescue arrived, they might have been able to keep cycling tanks.
Just throwing this out there as an alternative to SS or rebreather.
Any idea what the ambient pressure was at his location? The one news article says 22' below the lake, but the way news reports are written I can't conclude if that's 22' below the water surface or the bottom of the lake. I've only worked around small private water intakes in lakes, but none of them penetrated below lake bottom except very close to shore. They tended to lie near the bottom until close to the end, where they'd be off the bottom far enough to avoid sucking in sediments. None are underground in more than about 5-6' of water. Sewer outfalls are pretty similar: The pipe is usually exposed no more than about 5-10' deep (depending on tide).