It's a Federal law, abbrieviated HIPAA. I'd have to stop and think what it stands for. Go to your favorite search engine and search on HIPAA. BTW, it's barely possible that NY may haave a shorter look-back period than one year (my state does) but it CANNOT be longer than one year.
If you were covered under the old plan for less than a year, you still have to be covered under the new plan, but your wife's condition CAN (that is not to say that it will) be excluded for the period of one year minus the length of time you had coverage. For example, if you had coverage for eight months, her cancer can be considered a pre-existing condition for four months.
If there is a gap between the old and the new plans of more than 62 days, the new plan can consider the cancer as pre-existing for the full year, no matter how long you had coverage previously. Contractual waiting periods don't count; however, that's also what COBRA is for.
Again, I'd like to reiterate that not all insurance plans have a pre-existing condition clause, and the ones that do are limited to a maximum of 12 months.