When the mobile phone system was being set up, there was (and is) a part of the relevant law that said you couldn’t prevent companies from installing communications infrastructure.
When broadband came on the scene, some companies leapt on this as a way of forcing themselves into apartment blocks and installing their cabling (to the exclusion of rival providers).
But smart blocks hit back, saying okay, we can’t stop you from installing your infrastructure, but we still have a major say in how it’s done.
I’m guessing that quirk in communications law is what this provider is using, but they are trying it on. They need strata approval and, in any case, tenants shouldn’t be doing anything to common property.
If you want to nip this in the bud, hit the tenants with a bitll for repairs and order the broadband provider to remove their cables form common property. See what happens then.