The telecommunications laws do compel you to allow companies to have access to the block – but it’s not open slather. You are entitled to ask what their plan is and what changes that would make to common property, including the ability for other future and existing providers to operate freely and without any impact on their services.
A lawyer’s letter to them explaining that access will not be allowed until you have more detail about their plans and its impact on other services and common property, plus compensation they propose to offer for use of common property and electrical supply, would be entirely appropriate.