Shapefiles show the A-25 designation extending all the way to QC125_N/QC158_E.
While I didn't see any reassurance markers or a FIN sign north of Rang de la Riviere Sud, there's signage at:
1 2 3 4 5
I found the first SB reassurance marker a bit south of Rang de la Riviere Sud.
Just from the advance FIN signage on NB QC 125/158, I'd put A-25's north end at Rang de la Riviere Sud/Rue Montcalm. There is A-25 signage on side roads north of there, but I would discount that, since Quebec is often sloppy about putting Vers ("To") banners above markers for routes that don't quite reach that intersection. That issue threw off Tim when he placed A-640's east end at QC 138, but he didn't catch the FIN marker north of there at the QC 344 intersection.
Autoroutes often but don't always end at at-grade intersections like the one with Rang de la Riviere Sud, so that's not inconsistent with the shapefiles. But the advance FIN sign mentioned above seems to disagree with the shapefiles, so I'd go with the sign.
If I put the A-25 north end at a new RueMon (or RangRivSud) point at the traffic light, that point would need to be added to the QC 125 and QC 158 route files. This would be in addition to adding the missing point in the QC 125 route file mentioned in my previous post.