Stephen – as your Building was constructed in 2001, and if it’s in NSW then the By-Laws shown at Schedule 1 of the NSW Strata Schemes Management Act (SCMA) would apply, and the most relevant of those would be:
3. Obstruction of common property
An owner or occupier of a lot must not obstruct lawful use of common property by any person; and…
17. Appearance of lot
(1) The owner or occupier of a lot must not, without the written consent of the owners corporation, maintain within the lot anything visible from outside the lot that, viewed from outside the lot, is not in keeping with the rest of the building; and…
Under the SCMA, residents (including tenants) may not alter, add to, or erect any structure on the Common Property without the prior written consent by the Owners Corporation.
So in my opinion any or all of the above would provide the Owners Corporation (O/C) with ample grounds to issue the Pizza Shop Tenants with a Notice to Comply (NTC) with a By-Law; in fact issue them with two (2) NTCs – one for each By-Law non-compliance.
That will no doubt get the ball rolling by providing your O/C with the means to proceed to Mediation with the assistance of the NSW Office of Fair Trading, and depending upon the outcome, to the Consumer, Trader, and Tenancy Tribunal (CTTT) for Adjudication if the Pizza Shop Tenants do not comply with the NTC.
With regard to the unauthorised use of electricity, I assume you’re referring to the “house” or Common Property supply in which case I’d firstly suggest the O/C engages the services of an Electrical Contractor to determine whether or not that supply is correctly / safely / legally connected (e.g. extension cords to cool rooms would be illegal), and if it’s not correctly connected then your O/C should contact the local Electricity Distributor (the poles and wires people) about disconnection.
That in my opinion is a better approach than the O/C simply turning off the unauthorised electricity supply and thereby risking some legal response by the Tenants for loss of their cool room contents.
On the subject of legal responses, as OverIt advised (post #2) the Pizza Shop Tenants are occupying the Commercial Lot with the permission of the Owner and under the terms of a Lease, so they’re not squatters and any concerns about their occupancy of the Common Areas under “adverse possession” provisions are in my opinion groundless.
The provisions of the SCMA applies, and your O/C should instruct its Strata Manager (SM) to get off his ?*!^ and issue the NTC, which by the way your Plan’s Executive Committee will need to meet and formally resolve and minute to do, before then providing the above instruction to the SM.
Finally, who is the Proprietor / Landlord of the Commercial Lot, and what do they have to say about all this?