Your question raises two different issues.
1) HD stations on first adjacent channels can cause interference.  The digital component of the signal is effectively co-channel white noise.  The rules specify the protection ratio which must be provided to 1st adjacent analog signals when implementing HD.
2) There is a lot of documentation (including the International Telecommunications Union)  that indicates that vertically polarized signals are more susceptible to multipath cancellation where there are high vertical reflecting surfaces (i.e. buildings) or rugged terrain. There are stations in Vancouver which abandoned circular polarization and reverted to horizontal-only because of multipath issues.  
That said, it is also a fact that once a signal of any polarization hits a reflecting surface, the resulting polarization is random.  Otherwise a pure horizontally-polarized signal would be difficult to receive with a vertical whip antenna, which is what automobiles utilized before the advent of windshield antennas.

rk12 wrote:

Yesterday CFMU was pushed out by WWSE Jamestown NY hear in Mississauga.It depends where you are located.Both CFMU and CFXJ are low powered.

I am surprised you could receive CFMU in Mississauga. I can rarely receive it if I am travelling in east Oakville.

Is the CFMU transmitter still located at Mohawk College?