Is roaming charge possible to happen in area even not near US border?

there's no roaming charge if you "roam" on other canadian networks (bell/telus). 

you just want to make sure that your usage in these network do not go beyond 50% of your total montly usage. If you you go over 50% for 3 consecutive months (maybe 2... I'm not sure), Videotron may cut you from roaming on these networks. 

when in Ontario, make sure you are not roaming on US networks.

I was in the Canada Upper Village region... there was no or very low coverage on Canadian Networks where I was... and my iPhone was sometimes connecting to one of the US networks accross the river. I don't really mind because I have a Canada/USA plan... but I had a friend with me that didn't have that kind of plan... and he got the $6 roam like home option charged on his line for that day.