sure they can call, but 4ds can't share anything that hasn't previously disclosed to the market - that would be a clear insider trading scenario.
If they wanted to share new information with any suitor who hasn't launched a takeover proposal / bid - 4DS would have to make a market announcement (say a technical update) with that new information so as to avoid any possible insider trading scenario.
At the start suitor, would have to base their due diligence on technical updates, corporate presentations, market announcements and their own research...
If a suitor came to 4DS with a takeover proposal, then 4DS could grant the suitor DD access but this would usually be accompanied by a market announcement. Case in point look at Ausnet Services and the Brookfield's / APA takeover bids and recent annoucements.
https://www.allens.com.au/globalassets/pdfs/sectors-services/ma/takeovers-handbook.pdf
(20min delay)