We paid the right of permanent residence fee at the beginning, with the other fees, so they never contacted us about this. I'm not sure but I guess that asking for the RPRF and then issuing the visa quickly after that is usually for other classes, like skilled workers. That happened to me when my visa was ready to be issued and I was in the skilled workers class. But for family class sponsorships I don't think this would be the case, since we already had the option to pay all the fees upfront.
I haven't heard anything from themselves, but I sent them an email a month ago asking for my file number, which they replied after 2-3 days and gave us the file number.
Anyways, its good to know they have started looking and working on the April files.
Hope you see your husband very soon :-*