Depends on your definition of healthy.
By processed. Well by nature they are very processed Someone isn't lovingly crafting each one, roasting chickens to slice off the bone and fresh mayo. They go through all sorts of machines, and the various ingredients go through a number of processes in turn, with probably more ingredients than you add at home, to enable it to stay on the shelf for the full day without going soggy.
A healthy 'to-go' lunch is few and far between. Sandwiches are almost always bundled in a meal deal. So you're looking at I suppose an average of 500-600 including your crisps.
It isn't the worst option, swap your sandwich for a pasta pot, and you could actually end up with it being more. The salad pots also seem better but are often filled with high calorie ingredients to make them less boring.
But none of them compare to getting mcdonalds or kfc for lunch.... or even subway.
And it's not just looking at calories...a pasta pot might be higher in calories than some nuggets, but the pasta pot (hopefully) might contain more nutrients from veggies etc., and fill you up longer.
To be clear I know these places do have a healthy option; subway salads can be amazing and filling. But while you can get a healthy option, the temptation is there for a less healthy option, which when you're hungry and picking the first thing that you see, you have more high calorie low nutrient foods on the menu and therefore less likely to make a 'healthy' choice however you define it.