Your friend should be able to ask for compensation for medical expense (exclude those covered by OHIP or other insurance) , loss of income, pain extra. Two ways in dealing this, if your friend is only ask for medical expenses, the homeowner can use his Voluntary Medical Payment clause in his insurance coverage, usually its up to $2500. But if your friend is seeking for liability compensation as well, unless he can reach some agreement with the landlord. Otherwise he might need to get a lawyer to sue the homeowner.since usually the Insurance company will represent the landlord and they have expertise lawyers in those cases. However, the chance is high for your friend to win the case as he has witnesses and there is no doubt he's injured due to the landlord's neglegence. Good luck.