Quote: "It would be up to the company being audited to release the report whenever they see fit."
Exactly! The annual report is not automatically published when the auditors sign off.
Quote: "Other alternatives are the audit firm found glaring errors in the financials which took a long time to resolve. Or they haven't got paid yet."
I think these 2 alternatives are highly likely to be the cause of the delay.
Other alternatives include:
1) disagreement with the auditors 2) seeking a second opinion 3) auditors issuing a disclaimer of opinion or withdrawing from the engagement (worst case scenario)