I have also been researching this, and it is hard to find clear answers.
A couple of days ago I saw a backhoe on a trailer going up I-5 that actualy was following all the rules. It had 6 chains and 6 binders, 4 sets securing the machine, 1 on the front bucket and 1 on the rear bucket.
I have for years been only using 2 chains and 2 binders on our backhoe and D3 dozer. One looped through the rear hitch pin on the dozer, on the backhoe run behind the backhoe lower boom pivot attached to one side on trailer D-ring and then attached through D ring on other side with binder. On the front of the backhoe chain is run around axle and attached from one side to the other iwth one binder, dozer has a hook welded to top of blade with one chain from side to side with one binder.
For our excavator, CS563 rollor, 928G loader we use four chains with four binders. But have never chained down the bucket on the excavator or loader.
Looks like we will have to change our ways before we get a big ticket.
I did get pulled over awhile back for a safety check with the excavator, and they never said anything about the bucket not being chained down.
How long have these rules been in effect?
I did find something on the State of Oregon's "Federal Motor Carrier Safety Regulations" page, Part 390. Where it shows what was mentioned before about the one chain and two binders, and says it is legal.
http://www.oregon.gov/ODOT/MCT/LAWS.shtml
Link to JPG I made of the page for 390-130, showing a picture and description of the one chain, two binder setup.
http://www.zenitram-inc.com/Files/393-130.jpg