So the other day, when asked at the Subway drive-thru what I wanted on my BLT, feeling adventurous I simply answered, "mayo, pickles, and extra tomatoes." And that's how I found out that the bacon is implied. At least the sandwich had bacon. I'm not sure on the tomatoes--I may have just gotten the extra tomatoes but not the original allotment. And there was definitely no lettuce at all.
If my little public service announcement saves even one person from a lettuce-less BLT, then my work here is done.