Why Britain would not reclaim Halifax as a Royal Navy dockyard

Were there plans to restore Halifax as a Royal Navy dockyard after the Second World War?

No; Halifax was already a Canadian naval base, so its development belonged to Canada rather than Britain.

Britain operated Halifax as a Royal Navy dockyard from the eighteenth century until its closure and transfer to Canada in the early twentieth century. By the interwar and postwar periods it was a Canadian naval base, not a dormant British installation awaiting reactivation. Any major upgrade was therefore a Canadian government responsibility. The answer uses institutional ownership to correct a misleading continuity: a harbor can remain strategically important while the state responsible for funding and operating it changes completely.