Bava Batra 18: Who is Responsible to Move Away from the Boundary

A number of substances cannot be placed close to another person's pit.  The Gemara reasons that these things are damaging to the wall of a pit: 

• residue of items where oil has been extracted
• manure
• salt
• lime
• rocks

Perhaps these examples prove that dampness is damaging to the wall of a pit.  The fact that millstones are not permitted to be close to the wall of a pit may prove that vibrations are damaging to the walls of pits.   And if the oven can't be too close to a wall, perhaps we are learning that heat is damaging to the wall of a pit.  

The Gemara considers other directives: we cannot open a bakery or a dye shop beneath someone else's wine storeroom.   We cannot open a cattle barn there either.  But the rabbis argue that these conditions may be dependent upon whether or not a pit was already constructed in this place.  

The rabbis turn back to arguing about tree roots and how they might grow through rock and into another's field.  A plow must be able to dig three handbreadths from the boundary of a neighbour's property.  

We are faced with the example of two neighbours who say that the others' property impinges on their own: mustard plants and bees.  Each destroys the other's property.  The rabbis wonder who should have to bend to accommodate the others' concerns.  In the case of mustard plants and bees, the rabbis argue that the plant might not be irreparably harmed by bees, for bees can't find the seeds, and the leaves will grow back.  

Are these different halachot? Or do they all fall under the same category?  The rabbis argue this question.  Can we generalize that the one who causes the damage is the one who is responsible to distance his property/himself from the boundary of someone else?  This seems to be the case in simple circumstances.  When it comes to a case like the bees and the mustard plants where each may damage the other, the owner of the bees must move.  We are not told why this is the case, given that the bees might not even damage the mustard.  Perhaps it is because the bees are easier to move than the rooted plants.