It's certainly not bad to take a labor job. As combatmedic said, it's GPP (general physical preparedness).
As to working hard with the body... why else do we have them? It seems kind of pointless to spend a bunch of time in the gym getting strong... so we can spend more time in the gym getting... more strong.
Shoveling works the abs, low back, biceps, triceps, shoulders, upper back, hamstrings and thighs to different degrees depending on how you shovel. I remember reading something about how coal shovelers had great rippling abdominals, and you certainly have to keep your abs tight to shovel correctly, and it could help reduce body fat, as you're doing a lot of work (read, burning calories).
If you don't have a lot in the tank right after work, don't go right after work. Go before work. Or rest for a few hours and then lift. Whatever. I've found that just being off of work is a great tonic for how tired I feel.
Then again, I'm not working a construction job, so I don't know.
Anyway, good luck.
Dan "Anyone know about Shovelglove?" McVicker