Based on how few people I see whenever I've been on this southeastern section of Lantau (be it to hike or take part in beach clean-ups), I'm inclined to conclude that the length of that official trail puts many a hiker off in addition to its out of the way location. In either case, it's a real pity; not least because this part of Hong Kong really is pretty scenic, and there also being ways to break up the hiking routes so that one doesn't have to go along all 18.5 kilometers of the Chi Ma Wan Country Trail in one go!
As an example: the section of that trail which passes through an area known as "rock wonder" can be accessed without having to go up the highest points of the peninsula. Also, the Inter-Islands Ferry between Mui Wo and Cheung Chau makes regular (though not frequent) stops at a pier on Chi Ma Wan. So if you get your timing right, you can take that ferry back to civilization (as I've done more than once now), the trail head, or both!
Picturesque dwellings at Shap Long Chung Hau village
over on the north-eastern edge of Chi Ma Wan Peninsula
My hiking companion and I followed the signs to the now disused
correctional institutions but then headed beyond them to get to the section
of the peninsula that's part of Lantau South Country Park
View from the trail of Hei Ling Chau, an island that's home to
three correctional institutions and an addiction treatment center
A rocky section of Chi Ma Wan Peninsula
Further along the same trail, the more populated
island of Cheung Chau comes into view
Natural rock formation or modern art sculpture? ;)
Hike's end that day: the ferry pier near the now disused
Chi Ma Wan Peninsula correctional facilities! :)