An arborist could give you a quote for the work and could also advise whether the tree would be a ‘regulated tree’ or whatever the WA equivalent term would be. If it is regulated you might need permission to undertake a ‘tree damaging activity’ and again, an arborist could advise whether the pruning would amount to that or not.
Does the OC have a lot of trees? If so, I would have expected it would have some established practice for them such as a preferred tree surgeon and a line in the budget for their management.