Energy transfers back and forth between the strings and body, which is why the body can generally be expected to have some impact on tone. How much energy transfer goes on? I don't know, but you can use a mechanics stethoscope to at least hear what the vibrations sound like when they transition into the neck and body.
I also suspect that bridge placement makes a big difference in the amount of energy transfer that goes on. Electric guitars generally have the bridge near a node, so that limits the energy transfer somewhat. Basses have the bridge further back; partly that's due to ergonomics, but it also has the effect that more vibrations transfer to the body, which ought to reduce sustain. In a guitar you usually want more sustain, but in a bass too much can be a problem.
Nut material makes more of a difference on open strings, but in general a plastic nut is squishier and it absorbs more energy than something like bone, causing the note not to sustain as long. The saddle is the same way, but plastic saddles aren't typically used in electric guitar so it's not usually an issue.
I also suspect that bridge placement makes a big difference in the amount of energy transfer that goes on. Electric guitars generally have the bridge near a node, so that limits the energy transfer somewhat. Basses have the bridge further back; partly that's due to ergonomics, but it also has the effect that more vibrations transfer to the body, which ought to reduce sustain. In a guitar you usually want more sustain, but in a bass too much can be a problem.
Nut material makes more of a difference on open strings, but in general a plastic nut is squishier and it absorbs more energy than something like bone, causing the note not to sustain as long. The saddle is the same way, but plastic saddles aren't typically used in electric guitar so it's not usually an issue.