ND placed me on the "provisional list" near the end of Feb., and I asked them to remove my name from consideration in early March (hope that ends up helping someone). The provisional list is the same as the waitlist. As of Feb. 20th they hadn't ranked the list but I assume they will before taking candidates off of it (they said they will start doing that in late April but I know people who got waitlisted in Feb. then got an acceptance letter a few weeks later).
I think the best thing to do is send them a letter saying ND is great, it's your top choice, and how/why you value it over the other law schools you applied to. Also, be sure to mail in any updated grades, awards, etc. I don't think calling would do a whole lot, but that's just my opinion. Again, I think the most important thing is to let them know ND is your top choice (I'm assuming it is from the tone of your post).
BTW, I've heard a lot of rumors that ND is going to have a ridiculously low acceptance rate this year, something like 12%. I know that a ton of applicants got a letter asking them why they love ND yada yada (these people were not waitlisted, their apps were just pending until ND got their response), and that a lot of these people had superior numbers, like 170+ LSAT's. I think ND is using the provisional list and the "why you want ND" letters to weed out those apps who apply to ND as a safety, or have it as their 10th choice.
I bleed the blue and gold, and would have liked to go to ND. I was told by the asmissions office that there is basically zero chance of receiving scholarship $$ if you get in off the provisional list, so that's why I withdrew my app from consideration. Good luck to you, hope it works out.