When I was in outdoor large scale we used several systems and had no issues with unauthorized signals taking over trains. One show had many people running the same systems in same room and had no issues with pirated engines
RCS ,Airwire Piko and Aristocraft systems all worked exceptionally well their features and costs varied greatly
I liked Airwire as it followed DCC standards and was made for model RR hobby and you could use many different sound systems
We were getting very long run times with the new lithium battery technologies
The cost to build your own using RC plane and car motor speed controlers was cheapest way to go but less plug and play then other systems
some day I may just build one...