**Usual disclaimers about this not being legal advice and just the opinion of some bozo on the internet**
The starting point in a contractual dispute is to look at the words actually used in the contract – in this case the lease. We can probably assume from the fact there is a dispute that the lease isn’t clear about AFL games (pre-season or otherwise) being played by West Coast at Lathlain.
Where a term of a commercial contract is ambiguous or capable of more than one meaning, Australian courts attempt to give the contract a ‘businesslike and commercial interpretation’, and may have regard to the circumstances surrounding the contract, such as evidence of the background known to the parties at or before the contract, including evidence of the genesis and objective aim of the transaction, and pre-contractual negotiations (there is some complex case law on when a court can rely extrinsic information, but let’s just assume they can in this case).
I live in Vic Park, and none of the council Management Plans (see
here for example) mentions AFL games, and while there was consideration for things like parking and transport of Perth Demons games and West Coast training, there was no consideration for West Coast AFL games. That suggests to me that at least one of the parties (ie, Town of Victoria Park) proceeded on the basis it was just a training base. Objectively, if West Coast planned on playing games attracting thousands of fans to the game, they would have expected to have provided information about that at the planning stage.
In light of the surrounding circumstances, I reckon the Town of Victoria Park is in a pretty strong position. That said, as much as I loathe those bastards being in my backyard, the Town has benefited a bit from West Coast being there, so they’ll probably reach a negotiated outcome (ie, they’ll play there this time, see how it goes, and if West Coast proposes to play there again they’ll have to negotiated an amendment to the lease).