“Is it legal to use seed I have obtained from another province?”
The NB Cannabis Control Act only references under its "Cultivation" section specific rules around the # of plants, security required, and that only adults are allowed to do so. There does not appear to be reference specific to the seeds. Within New Brunswick, only Cannabis NB is legally allowed to sell cannabis seeds. However, if seeds have been obtained legally from another province, there does not appear to be any law within the NB Cannabis Control Act that would stop you from cultivating those seeds.