Suppose players A and B control the following tiles:
Let's assume the two A tiles and the 2 B tiles are in different territories.
Could a hero move from one A tile to another?
Yes. See the image below.
The example you are referring to is illustrated by the Yellow peasant on the right side of the board. The peasant could move to the forest square down and to the right from its current location. The red peasant would not hinder that movement.
Note that the same is true of the Yellow queen in the lower left. She could move to the corner in the lower left.
No comment on whether those are smart moves in this case.
Let me know if that does not answer your question.