Two of the four universities do have stated homeschool admission policies (quoted and linked). The other two do not mention homeschoolers so I have emailed the admissions departments and I will update when I receive a response. They both have mature student admission at age 21, and the University of Brandon appears to accept a GED in place of a high school diploma, should you choose to go that route.

University of Winnipeg 2010-2011 Admissions guide (pdf download)

Home School
Home-schooled students will be considered for admission to The University of Winnipeg on an individual basis. Each applicant must provide proof of completion of Grade 12 or its equivalent including Mathematics and English.

Canadian Mennonite University Home School Admission Page

Home-Schooled Students
Home-schooled students who are 21 years of age or older may be considered for admission as Mature Students. Students who are under 21 years of age and have not, or will not, receive a certificate of graduation through a public or an accredited private secondary school system, may apply for admission under one of the following two options:
Students who have successfully completed a provincial secondary school study program must submit a final mark statement and a graduation certificate from the Department of Education of their home province to demonstrate that they meet CMU’s regular admission requirements.

Students who have been home-schooled on a private basis must submit a written declaration or transcript prepared by the primary educator outlining the secondary level courses completed, the type of program, material used, and the length of the program. To be eligible for consideration, such students must have achieved a minimum of 60% or “C” grade average. After the student has completed a minimum of eighteen credit hours of coursework, or at the end of the first academic year, whichever occurs first, the student will be evaluated in accordance with CMU’s academic performance policy and the student’s status will be changed to regular status if the student has achieved a minimum GPA of 2.0, or to probationary status if the GPA is less that 2.0. The student must fulfill the Academic Writing Requirement within the first term of study.
Students admitted as Home-Schooled students are ineligible for Academic Entrance Scholarships, but they may be eligible for a Leadership Scholarship or one of the Specialized Entrance Scholarships in the areas of music, athletics, or church service.

Brandon University Admissions Page

According to Brandon University’s admission website, students may apply with a GED or a mature student in lieu of a high school diploma. No specific homeschool policy is indicated. I have written to them to ask for further information.

University of Manitoba Admission Requirements Page

According to the University of Manitoba’s admission website, students may apply as a mature student at age 21 in lieu of a high school diploma. No specific homeschool policy is indicated. I have written to them to ask for further information.