There are, to my knowledge, 2 insurance companies that provide insurance to paintball fields in Canada. Most paintball fields that are now offering airsoft have gotten a special 'rider' attached to their policy to allow them to hold airsoft games under their policy.
I would suggest contacting a local paintball field to find out who their insurance broker is and contact that insurance company.
The Tier One Tactical Operator
Tippmann Arms M4A1
KWA USP .45, KJW P226, KJW hi-cappa