I use Cedar (Ashe Juniper) all over the place as mulch, in buried wood beds, etc and have had no problems except when chips are mixed into the soil without adding extra nitrogen. I let the chips and logs weather a long time ( a year or more) before putting in beds, though, to allow any toxins to dissipate. Fresh chips make good pathways.
It is the sap you have to be concerned with, this is found only in the cambium layer of the tree and the roots.
So, if the tree is not a fresh cut (has had time for the sap to congeal and or dry up completely) there isn't anything allopathic left.
The leaves (needles) will create a little acidity if they are fresh and water (rain or other) flushes through them.