Landlords have a legal obligation to notify the OC that they have tenants and who they are, subject to a maximum fine of $550 for failure to do so (see section 258 below).
You could ask the strata committee to undertake an audit of all the lots to reveal which ones are unnotified tenancies and then pursue the landlords.
When the committee refuses, and they will, you seek orders under section 232 at NCAT, requiring them to fulfil their legal obligations by either finding out who has registered or seeking fines for those who haven’t.
You could also just seek mediation at Fair Trading and raise the issue there. Or, as you say, get a friendly owner to do the search for you.
258 Tenancy notice to be given to owners corporation of leases or subleases
(1) If a lot is leased, the lessor must give notice of the lease, in accordance with this section, to the owners corporation not later than 14 days after the commencement of the lease.
Maximum penalty: 5 penalty units.
(2) If a lot is subleased, the sub-lessor must give notice of the sublease, in accordance with this section, to the owners corporation not later than 14 days after the commencement of the sublease.
Maximum penalty: 5 penalty units.
(3) If a lease or sublease of a lot is assigned, the assignor must give notice of the assignment, in accordance with this section, to the owners corporation not later than 14 days after the execution of the assignment.
Maximum penalty: 5 penalty units.
(4) The notice must be in writing and specify:
(a) the name of the tenant and an address for service of the tenant, and
(b) the date of commencement or assignment of the lease or sublease, as the case
requires, and
(c) the name of any agent acting for the owner in respect of the lease or sublease