There are at least two backcountry trails that the people working at the Whistler Olympic park know about. And there are signs along some of the cross country trails which point to these trails.
There are 2 possible access points for the trail. (The trail proper starts when you leave the groomed run just west of the maple leaf bridge over Beverley Creek. There are two ways to get there:
#a. Park at the Whistler Olympic Park Biathlon Range.
Head northwest on the groomed trail, passing under an overpass (barely visible on satelite), and then curving around a hairpin to head south. (see satelite photos). Just as you curve south, there is a rough connector trail that cuts off and goes down through the trees to connect with the Madeley Loop which is below you and to the west. Once you emerge from the tree connector, onto the groomed Madeley loop, ski up it's edge till you reach the XC bridge over Beverley Creek. We refer to this as the "Maple Leaf bridge" because it has 4 metal cutouts of maple leafs on it. Once across the bridge, you'll see signs for the Beverley Creek Cross country route on your right. Here you leave the groomed Madeley loop and head upwards into the trees, following the orange markers.
#b Park at the Alexander Falls Parking lot
From here ski along Madeley Creek Loop XC trail to the Beverley Creek Bridge, about 2km. Just west of the bridge, pick up the trail in the forest on the righthand side. There is a designated snowshoeing trail (Madeley Explorer) that runs parallel to the Madeley Loop XC trail. See East Madeley Route.