It is worth keeping an eye on the link I have attached. At the moment I can see that there are Oath ceremonies tasked in Winnipeg for March 28, 29, April 5, 12, 14, 18 and 26. The Winkler location is showing Oath ceremonies tasked for April 26, 28, 29. April 5, 12, 14, 18 and 26.
This online link allows you to see forthcoming information. It is usually updated monthly, and shows the regions throughout Canada. Note: for the temporary offices (where a permanent site does not exist) a separate link exists.
https://secure.cic.gc.ca/CeremonySearch/search-recherche-eng.aspx#resultList
If you ever get notice via email that a date has been sent for test / Oath, and the email states a letter confirming the date and time has been sent and you subsequently don't receive it, I personally would follow up with the CIC helpline if I were you. My understanding is that CIC should give a minimum of two weeks notice of tests and Oath ceremonies. I have seen some applicants from other months get just two weeks notice, while others get a month or more.
I hope this helps.