I am uncertain about the sections that lack GPS traces, which are the only ones I have local knowledge about. The sections with GPS traces are still used regularly, but. the disused trails in the area have become overgrown in recent years.

The trail to Chadsey Lake has been hiked as recently as May, 2018. It is a popular trail used by geocachers.
Access names are gleaned from posted signs on the paths as well as the crowdsourced Sumas Mountain Trail Map at https://www.trailforks.com/