While the wording in the act could be interpreted either way (i.e. "has been admitted to
canada for a 1-year or greater period", or "has been in canada
legally for one year or more") CIC policy is quite clear that it is the former interpretation that is in use.
OP1 section 5.17 explains this.http://www.cic.gc.ca/english/resources/manuals/op/op01-eng.pdf
"5.17 What is meant by “lawfully admitted”
3. R11(1) also stipulates that an applicant must have been lawfully admitted for at least one year
when applying for permanent residence
Persons who are applying for permanent residence must be residing in and have been legally
admitted for a period of at least one year to the country which the visa office receiving the
application serves. The applicant is not required to have been residing in the country for one year
at the time of application, but to have been lawfully admitted to that country for a minimum one-
year period at the time of application.
For example, under R11(1), an individual may have lawfully entered and be currently residing in a
country on the basis of a one-year work permit. Anytime during that year, the individual would be
eligible under R11(1) to apply for permanent residence to Canada through the visa office
responsible for applications from the country in which the individual is residing."
So what matters is not your original entry into Canada, but whether your current status is granted for one year or more. If you have a 1-year or longer work permit, study permit, or visitor record, you can apply to Buffalo. If you do not, you can't.