Dont hold me to this, If you check with Thatcham who crash test they will be able to tell more, but for the vehicle to get a certificate, ie a crash test certificate, the vehicle has to be a specific vehicle, ie Ionics use Renault, and it has to be tested from the front, back and both sides, that means 4 vehicles, for each models, ie long wheel base, short wheel base ect ect which cost alot of money, and thatcham charge for the test obviously. I think as long as the system is bolted down through the floor and you have a decent bafled tank, and it is installed correctly, you should be fine. I personally would not trust straps to hold a tank down. When i was at windex i was impressed with both systems, Ionics seem to market their system better, i was also impressed with the Tucker system, the guys did know what they were talking about, and they have a background in water purification and you get slighty more for less money.
Im also still debating between the two systems, and at the moment im still very undecided!!!
Thats my opinion.