Hi, I dont think the OP intends for the ETP to not be on the outside of the house, the question is, can the leadin from the street come up through the slab and access the ETP from behind (ie from within the wall), the feed out to the ONT would be similar but obviously not go via the slab but via a conduit up into the wall and off to the ONT.
In my view there is no problem with doing this, what may be an issue is sharing a hole in the slab with the water main. Technically I dont see an issue with water and fibre sharing a hole in close proximity, however the plumbing regulations may.
Cyril