Sometimes I come across old TC adds, and it never stops amazing me the things they used to make. I can not confirm that 1:60 is a factory twist for a New Englander, but I wouldn't bet against it. I actually think it is 1:66", but close enough. Most, if not all were 1:48". Their carbines were usually 1:20", although even the scout rifle carbine came in a slower twist once in a while. Possibly that 1:38". It's also possible that the guy has another model that happens to look like a New Englander, but really isn't. I know I've seen a pistol grip version of the New Englander, but it wasn't called a New Englander. Everything else on it looked the same. I'm fairly sure that was a slow twist.
TC definitely made slow twist barrels, although rarely, but from what I've seen they were all shallow button rifling, so I doubt the very slow twists are any better off than the 1:48" standard, which works fairly well. The only 1:20" twist I have is the scout pistol, but that would be plenty accurate for 75 yard shots with a rifle stock. It really doesn't seem to shoot that much different than my 1:48" Renegade, although being a pistol, is much harder to test accuracy potential.