An APU will probably not benefit a team operation very much unless the truck sits around a lot. And even then, with the little amount of sitting around that teams do, the benefits would not be in fuel savings. At 10 grand, it would take a lot of sitting around with the APU running to pay for the unit in fuel savings. The benefits to a team truck would simply be in keeping maintenance & down-time costs down on the truck's extremely unreliable emissions system. Fuel doesn't burn completely enough at idle, so it puts more "global warming" in the exhaust, which causes even more problems then those systems have already.
And
@SkateBoard is wrong about there being no need to keep the big engine warm as long as your batteries are good. He runs a pre-emissions Detroit 60 engine & never plans to replace it with anything newer, so he has no reason to really educate himself much on the emissions systems or even think about them much.
Cold engines are even worse at not burning the fuel completely, especially when it's a diesel that relies on heat to ignite the fuel instead of a spark. In winter, you're going to be blowing unburnt fuel into the emissions garbage whether you idle it or not, because if you don't idle it, you're going to be blowing that crap into the exhaust when you fire it up in the morning, until the engine warms up.
Keeping the oil warm is good for any engine, but if you can keep the upper cylinders warm too it's the way to go with these modern engines as far as the emissions systems are concerned. And the best way to keep the upper cylinders warm would be to circulate hot coolant through it.
I think Skateboard's got the best APU setup in this case. He doesn't have his cooling systems tied together but he's got both an AC generator and a 60 amp 12 volt alternator. Using it's alternator he can maintain his truck batteries but if he needs lots of power to run several block heaters all at once, or run a big 200 amp booster to quick-charge the truck batteries in an emergency, he's got the power available. And he can run an electric block heater too, he just doesn't want to because he had some back luck with one.