Yes I confirm, they closed the bridge for safety issue. Here is what the snowmobile club published on Facebook about that:
Following a thorough inspection, we made the decision to completely close the Mattawin Bridge. The bridge is not safe enough.
You will have to borrow the bull dam Taureau. The change has been reported to the federation and will be visible on your snowmobile app(imotoneige).
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And yes the crossing on the dam Is ok now it have been reworked, the central section is wider and pretty straight on the west side.