In a word, no.
Add supermarkets, most ferry terminals, hotels with attached bars, etc., to that list. Also department stores in most cities (but never on the ground floor!). If you're in Scotland in warmer weather, you may find a port-a-loo at construction/roadworks sites. Hostels are another good option, as are distilleries (Thank you, Talisker!).
You have to take in to consideration that out in the hinterlands, there are no sewer mains, so it's expensive to create a septic field.
Skye, in particular, is becoming overwhelmed by the lack of public toilet facilities, but there are currently no plans in the works to build more.
I've never seen heather tall enough to hide behind, unless you squat really really low!
If you're bothered by frequent need for the loo, it's best to plan your trip around the Highlands and Islands very carefully. It can be done. Generally, if you're driving, you're never more than an hour away from some sort of facility. If you're hiking, it's a whole other situation. I've been there!
p.s.: For anyone familiar with the long running comic strip "The Broons," as seen in the "Sunday Post" and countless annuals, please note that they have no toilet facilities in either their flat on Glebe Street, or at the but 'n' ben. So we have Maw, Paw, Granpaw, Daphne, Maggie, Joe, Hen, Horace, the twins, and the bairn all living in one flat with apparently no toilet. Perhaps there's a cludgie on the landing, but it's never mentioned. Also, no toilet at the but 'n' ben, either. Ouch!!
p.p.s.: For politeness sake, best not to ask for the "cludgie" in Scotland if you're seeking toilet facilities.. :)