Hi Sean:
Don't know about the changes to any CTC standards but I've noticed that the newer hay ricks around here have ackerman steering. One of the problems is that it is easy to overload wide spaced axle trailers and then the trailer gets its own harmonic going which can end up steering the tractor!
Worse than a tag-along with too much tongue loading!
I always thought that was why the British and Canadian Bofors used a narrower front axle... in order to save costs and production time they used wagon steering but compensated by using a narrower axle. An automotive engineer's opinion would be welcome. I can tell you that from a Gunner's point of view the narrower axle is a pain in the bum as you are creating another set of ruts and accompanying drag when you are going through mud, snow or sand. I've actually gotten the LAAT and Bofors stuck in our own backyard during the spring thaw... what a mess!
Cheers! Mike