I tried riding the dirt roads through Moose Mountain on three separate occasions. Each time I had to turn around : too muddy and wet.
It takes forever to dry out, and to make it through, you will need a long spell of dry weather/ little rain, before its passable on two wheels. I would like to eventually do it someday.
There's a cool route you can use as an alternate from Oxbow, south then through the Souris valley ( gravel ) that will connect you to Estevan and hwy 18.
If the water is high, there is a low level crossing that will be impassable . I know one rider who tried it and lost his bike, had to swim back to the road and walk out!!!!
Souris Valley just east of Hwy 9