2.4 GHz is a licence free band. A few years ago it was largely empty, but now it is getting full.
I've had to change the channel of my home network a few times to maintain a good connection due to neighbours installing their networks and not knowing how to do it themselves.
If Bachmann use 2.4 GHz and if they hard-wire in the channel or sub frequency then we're going to have problems. Frequency hopping is one solution, but it is expensive. Channel selection - perhaps using DIP switches is another solution.
Zimo use 433 MHz (in Europe) which is designated as Industrial, Scientific, Medical band. Perhaps Bachmann/ESU will do the same.
For the USA, they will have to use the 900 MHz band.