"Normally, Catholic education is separated because Catholic educators don't want the students to have any contact with non-Catholics."

I disagree with this assessment. Decades ago there were sufficient numbers of young people even in smaller communities to render parallel school systems viable. Now that's changed, particularly in smaller communities and rural areas.  It seems to me that both sides likely want to maintain their enrolment numbers in order to justify funding and infrastructure. In the Saskatchewan case, it appears that public school officials are trying to prevent non-Catholic students from being funded to attend Catholic schools rather than the other way around. The viability of the public school system in some areas is obviously under threat. To get around this, and short of constitutional change (which should be examined), perhaps sharing resources in consolidated school buildings that accommodate all students is a good option that all sides should consider.