Hmm, regardless of whether or not they serve veg options, I still view these corporations as being somewhat 'evil', if you will. Their advertising campaigns border on brainwashing, they commit unspeakable atrocities against animals, are thoughtless and damaging towards the environment, encourage poor health and obesity and have played a major role in creating a society in which very few people are educated or conscious of nutrition and health.
Sure, if I'm in an absolute pinch, I may go order a meatless, cheeseless, mayo-less burger from HJ's, but as a rule, I do not think that I should support them simply because it may contribute to the inclusion of more veg options. The few fast food chains which do offer veg options only offer vegetarian foods, not vegan foods, usually only have one option on the menu, and that option is usually unhealthy, and laden with as many non-flesh animal products as possible, as well as far too much salt, fat, sugar, and preservatives which are known only as a series of numbers.
When I want junk food, I have at-home junk food like nachos, enchiladas, muffins, cakes, hot chips or wedges, etc. I'll concede also that it is not unheard of for me to give up and have Subway because Midland Gate's food court is far from vegan friendly. However I do not believe that supporting these corporations as a regular practise is a beneficial thing to do in any way.
/rant. Sorry for the long post.