Reserves 14yrs (still serving)
I think the biggest issues will be enviro, unless you can prove the BBs are enviro safe and will break down, it will be a no go, any time I have dealt with Range staff, be it RSOs or Range control personnel ie: Commissionaires, the BBs left behind would be considered sacrilegious!!!
Also have civilians on DND land would not happen unless supervised, there is no way they will risk an injury on DND or damage to DND properly, I know this because 2 or 3 yrs back I had a very good friend that was our OPS WO, he was the one that made things happen in the Regiment as far as training went and as a former Para Reg Member and 3PPCLI he had a little pull through his own contacts, unfortunately Airsoft on DND land was not going to fly!
Anyhow, wish you luck, cant hurt to ask.