> If you look around, there a lots of articles about problems when delivery systems are used to transport ammonia, and then propane.

That's most likely related to meth production. They steal anhydrous ammonia (usually from farmers) and try storing it in propane tanks which are not designed for that. The tanks corrode or crack and then leak or explode.

I've also heard of farmers crashing their tractors into ammonia tanks or train cars of ammonia derailing, but generally speaking, the storage and transportation of ammonia is a solved problem. It's been used for industrial purposes for around 100 years and for agriculture since the 1950s. Based on on what the article said about NOx pollution and aftertreatment systems it's unlikely it will ever be viable for autos or any personal use where safety or risks are more of a concern than they are currently.