As of January 1, 2011, if you're driving a vehicle over 10,000 GVRW with commercial plates, you will be required to have a physical similar to a CDL (commercial drivers license) holder, and will be subject to random inspections. I work for a utility company; a co-worker was driving a ford F450 with an altec bucket system on board. He was pulled over today, and given a courtesy warning, stating that next year the requirements change.
This pertains to landscapers, utility workers, tradesmen etc. Ask the right questions of your employer, or research the law if you're self employed. From the OSP's point of view, the driver is responsible. I personally haven't seen any info on this yet. I'm sure I'll be covered by my employer, and I can post details if anyone's interested.
Molon Labe
Bigohio