Wow! Based on personal experience I can't recommend towing without safety cables--break-away system or not.
My second long trip with my new RV and new tow set-up last year. Traveling south in Florida on the Ronald Reagan Turnpike--just about to merge onto US1 down to the Keys. Late afternoon, heavy traffic, running about 65 on the inside lane. Felt a twitch, glanced in my outside mirrors, and saw about 1/3 of my Jeep Cherokee sitting outside the plane of the RV in the passenger side mirror. It was trailing straight and steady, but I happened to be on a long bridge with no shoulder and the Jeep was running about 6 inches from the concrete bridge railing.
I managed to gradually slow the RV and was fortunate that an exit was only about a quarter mile away. Made the exit and found a good-sized vacant parking lot in an industrial area. During all the maneuvers the Jeep stayed to the right of the RV, but tracked steady and straight behind me. I found the pin missing from the tow bar connection to the Jeep on the passenger side. The driver side connection was fine, and the Jeep was being towed by the one tow bar arm on the driver side and the safety cable on the passenger side. The driver tow bar arm was skewed way over and the passenger safety cable was taunt. When the pin dropped, the Jeep had moved as far as the safety cable would permit, but could go no farther, and simply towed straight behind me from that point--it was well outside the plane of the RV. My break-away had not stretched enough to activate, since the Jeep didn't come loose but had just moved to the side.
I have no idea what could have happened with the pin. It was securely fastened with the hairpin clip in place, and I always check the hookup at every refuel and other stop. It had to have either broken or somehow lost the retaining clip and worked out. I didn't have a replacement at the time, but unhooked the toad, located a NAPA, and was able to buy one. Have put about 5000 towing miles on the rig since then with no additional problems.
I'm not sure what would have happened had I not had the safety cables hooked up--but it wouldn't have been good. With only one tow arm attached, being pulled from only one point off center, the Jeep would have surely whipped around in that heavy traffic. I suppose the other arm might have broken and the break-away then activated the brakes, but there's no way the situation could have worked out as well as it did. I've had my one allowable "beginner's luck moment" and I learn quickly. You'll never see me towing without my safety cables.
Mike
