Neil, before I flame you, I'm going to tell you something important, so listen. This isn't a joke about feces, bees, or saturated fat.
When you eat, and you maintain weight, whatever level of calories that you eat that maintains your weight is, by definition, your maintainance level of calories. It doesn't matter what the calculations say, what the politicians who made the food pyramid say, or even what your beloved Dentist-Mentor said about calorie intake, if you maintain your weight at a certain level of calories, that level is your maintainance. Q fucking E fucking D.
That being said, if you've been dieting, this will throw off what's been going on. You have to have been maintaining your weight for at least a few weeks before you have any clear idea of what your maintainance levels. Any sort of calculation, equation, or tarot reading about your calorie intake is just an educated guess. Educated guesses can be close, but they can also be completely wrong. For me, massive eating guidelines are pretty freaking generous. For other people, they're right on. So you have to ADJUST.
As Joel Marion pointed out in his "Update" thread in the Photo forum, you should maintain for a few weeks after you finish a gaining cycle before you go straight into dieting. I would say the opposite is true as well--you need to maintain after dieting so you know where that level is before you go straight into a gaining phase. Otherwise, all those extra calories are just ready and rarin' to be stored as fat. Yes, I know that we do a lot of work here with nutrient partitioning, but the fact remains that after a long diet, your body is just ready to lay in some fat. There are technical reasons for this, but just suffice it to say that you need to maintain for a while before you jump into a gaining phase.
So when something tells you to eat 1000 calories above maintainance, what you do is the following: take the level that you have been maintaining on--because you should have been maintaining for at least a couple of weeks--and add 1000 calories to it.
Therefore, if you have been maintaining your weight on however many calories, that is a level AT maintainance.
It's not rocket science.