2-year MLA programs for a student with a pre-professional landscape arch degree?

I’m a little fuzzy on exactly what you’re asking.  The purpose of accreditation is to ensure that graduates meet a certain competency level – they’ve been exposed to a core set of skills and knowledge that is necessary to be an LA.  If your B is accredited, then you’ve got that.  If it hasn’t, then you may or may not meet those requirements, and it’s up to the M program to evaluate your education to see if it meets the standards or has some gaps to fill.  If it does meet them, great, you can be done in two years.  If it doesn’t, then well maybe you have to take a couple of extra courses to fill in the gaps and it will take more than two.  I don’t think you’re going to find any program that will guarantee a two year completion without an accredited degree UNLESS they’re already familiar with the curriculum of the non-accredited degree.  Even looking at your first two examples, that’s how I read those programs to work.