Hey slhall,
Acceptance into Canadian schools is a little harder to predict than acceptance to U.S. schools, so it's difficult for me to give you what I would consider a confident estimate of your admissions chances. However, given that you are very close to last year's median numbers, I would put this school in the range of "target" schools for you, which means that you have a good (although not excellent) chance of getting accepted based on the credentials you listed. Given that the LSAT is often weighed more heavily in admissions decisions (both for U.S. schools as well as those Canadian schools that accept it), if you can get your score in the 168+ range that would increase your chances nicely. Of course, make sure to really focus on all of the other parts of your application; your numbers should be complemented nicely by any essays you are required to write, and your résumé/CV should make sure to focus on your academic achievements, extracurricular leadership positions, and any unique personal traits or hobbies that you feel would make you stand out.
As to why the school might suddenly choose to allow students to submit the February LSAT, it's hard to speculate. It could be many reasons: they may not have gotten sufficient applications yet, and want to broaden the pool by letting students take a later LSAT; they may have received so many requests for extensions that they thought it would make it easier if students could just take the February LSAT; they may want to remain competitive with other schools which accept the February LSAT. It's difficult to say, and you shouldn't try to worry about it too much. Note that they do say that they strongly recommend that applicants take an earlier administration, so you're actually doing exactly what they suggest.
As to what this might do to your chances, I don't think it will affect them very much (in fact, it might actually give you a boost). Keep in mind that, when it comes to law school admissions, the earlier you submit your application, the better. Waiting until the last second typically ends up with you competing for a much greater number of students for a much smaller number of available spots. The fact that you will be among the earlier group of applicants due to your LSAT date is a good thing, and will let you get your application in ahead of the rush that might ensue due to the school's sudden allowance of February LSAT scores.
In any case, I would strongly recommend that you don't worry about why they added the February date or what this might do to your chances; both of these are things that are out of your control. Instead, focus on doing as well as you can on the LSAT, completing your applications in the best way you can, and submitting your file as soon as your LSAT score becomes available. Then you'll be giving yourself the best chance of acceptance.
I hope that helps! Please let me know if you have any further questions. Best of luck on the test tomorrow!
