According to Harry Muscle :
I'm going to be rewiring my house soon and because of the layout of my
house, it looks like there's going to be a handful of areas where it
will be easier to run a circuit to a junction box and then branch off
all the connections for that ciruict from that one juction box. That
means there will have to be around 12-14 wires comming in and all be
connected to the supplying wires. This makes me think that a bus
connection would work best, like the ones that exist in the breaker
panel box.

So my question is ... does such a junction box exist? One that already
has bus connections build into it? Also, is my idea up to code? I've
studied the Ontario Electrical code and I don't see anything that would
say that I can't do this ... as long as I don't overfill the box.

It'd be code, but as mentioned elsewhere, such junction boxes aren't
available commercially, so you have to make them yourself.

You _could_ go to the trouble of using, for example, regular metal
boxes and suitably rated terminal strips as the commercial/industrial
electricians do. You'd be doing your own "custom boxes".

However, the equipment isn't officially certified for it, and you'd
have to have unit-approvals (on _each_ one) done by Ontario Hydro
(or whomever they suggest) at something like $75-$150 _each_.

It's usually better to utilize a string of ordinary (deep if necessary)
J boxes (giving attention to the accessibility requirements) to cut down
the number of wires in each box. The parts are cheap and rated
for it. Just a bit more labor, and (perhaps) obnoxiousness w.r.t.
accessibility requirements.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.