Public Mobile is prepaid, there are never any so called extra charges. If you have already purchased a service, it will work. If you don't have a particular service and try to use it, it will simply not work. This differs from post paid services that will let you use any service even if not part of a plan package and ding you with pay per use charges.
With that explanation out of the way, data is Canada wide, so you will have no problem using data anywhere in Canada, so long as you have a cellular connection of course. For the province wide calling plan, calling is still available when you travel out of the home province. Calls can be made within the province that you are in. So, those in province calls would not subtract from the long distance add on. Unfortunately, once out side of the home province, incoming calls are treated as long distance and so minutes will be taken from the add on when calls are recieved. You did not mention SMS, that service is Canada wide just like data.
