An outlaw driver will be an outlaw driver whether there is an EOBR in the truck or not. Drivers determined to cheat will find a way to cheat EOBR's just as they found ways to cheat the books, especially if carriers are complicit. It's not like EOBR's force outlaw drivers to go through the scales.
What's the penalty for having an EOBR in your truck but suddenly discovering that "it was working just fine just five minutes ago, officer, I don't understand why it is a dead brick now." Given the rewards an outlaw driver may perceive in running an outlaw load, that possible penalty may be a risk worth taking. Just avoid the scales, don't have a wreck and you're good to go!
Most shippers and consignees don't care if there is an EOBR in the truck. Motorists don't know the difference. Cops can't know unless the truck is stopped and the EOBR is inspected. If someone wants to run under the radar and is willing to break the rules, there is little to stop him or her.
The people who distrust truckers will get around to dealing with that too. Coming soon to a truck near you: cameras that ID the driver and monitor his or face to guard against fatigued driving. Show too little eye movement too many times and the truck will slow down and then shut down so you can get the sleep you need.
I agree, Zorry, that FCC may not be the best case study about the effect of EOBR's on the level of truck crashes because, as you mentioned, it is not an industry-wide study. On the other hand, the FCC numbers do in fact show that with a compliant carrier, EOBR's made no positive difference in crash rates.
To support the point you are making, an industry-wide study would be required. Someone who is interested in doing that at an amateur level could capture the numbers now and wait a few years to compare them to the nubers when EOBR's are fully mandated and installed.