Will the court call a witness for the defence?

It's unlikely. In R v LS (2021 ONSC 4429), the defence was looking forward to cross-examining a witness. The Crown changed its mind about calling her. The resourceful defence, relying on R v Finta (1994 SCC 129), asked the Court to call the witness. The Court decided the circumstances were "very far removed" from those of Finta:

In our case, it is not at all necessary for this Court to call A.C. as a witness at trial. The defence is perfectly capable of doing so. In fact, the defence has the fortunate assurance of knowing that A.C. cannot easily resile from the evidence that the defence wants to elicit at trial because I am told that the said evidence is contained, expressly, in the statement that she gave to the police. Hence, the full toolkit will be available to Mr. Edgar, experienced defence counsel, including sections 9(1) and 9(2) of the Canada Evidence Act, RSC 1985, c C-5, as amended, if necessary. (23)