Interstate Load?

I wouldn't think so. Being that your trucks are not rated for CDL's.
That is a great question though, and one that should be asked of the local DOT.
Here, you will get many, many responses, a few of them might even be right. Most of them won't be however.

 

You are exempt from the CDL program 26,000 lbs and under. You need a Class B license to drive the 29,000 GVWR and 21 years old to cross state lines with a CDL. If a company is engaged in commercial enterprise and they use vehicles of 10,001 lbs or more, the only requirement is it's drivers must have a DOT medical card.

I'm sure the company is pulling a quickie with the 29,000 GVWR truck as you said it has an Ohio address and being a couple hundred feet in MI. The odds of getting pulled over in MI are nil.

But you are correct, they are in violation with that 29,000 lb truck if they let someone with less than 21 old age and a class B drive it across the line. I would bring it to your bosses attention. They can't force you to drive that truck either.

My understanding is you have a MI license. All it takes is one accident or pull over in OH and you will have some answering to do. But you could always move to OH within 30 days change your license and they couldn't do anything.

So you see it's one of them things you could get in trouble, but then you could get out of it. The company would of been better off if they didn't buy that truck.

Pour some sugar in the tank, lol.