Yea you can ride horses there. They have a designated trail system for them. I think the club name is redwater range riders. Look them up they should have a map
I wouldn't want to ride out there on a horse unless like mentioned there is a totally separate area where the horse and quads/bikes wont be around each other.
This is a Garmin GPS MAP with tracks that I made allong with others of the Old Redwater Natural Area in 2008, the area South and West Outlind in Red is the Area that was Fenced off to keep ATV/UTV/Motor Bikes OUT of the area to allow for Horses and others that did not want to be in conflick with the the POWER MACHINES. I have never been in this area so I cannot help you with any trails that are in this riding area.