I noticed this (http://imgur.com/LFnPyPv) happens if you have a railway between two RHWs and drag a perpendicular stub out of or into one of the RHWs in a way that triggers autoconnect. Heck, it might not even need to be a perpendicular stub.
This suggests some things:
1. Dirtroad's autoconnect is an entire script that's completely independent of the Street autoconnect (I haven't seen streets doing it AFAIK)
2. Said autoconnect is therefore intentional, and appears to be in an alpha state
3. It is possible dirt roads were intended to interface with rails in some way at some point; this may also explain why intersections can create override networks, and why commercial and industrial (which may possibly share the exact same code pointer in this specific area) can only interface with it if it's being overridden.
Of course, all of this is just a strange hypothesis I came up with. Feel free to speculate.
The streets have the same auto-connect behavior.
But what's the point of having a rail crossing at every tile then? Does the rail have autoconnect too or what?
Could you just embed the images instead of linking them every time?
AFAIK intersections create "new" networks by utilizing RUL flags that are setup around intersections in order for the simulation to track Sim behavior around said intersections and monitor traffic flow.
The weird behavior is likely due to the fact that Rail is coded as an enabler for the RHW. If Ganaram were here, he might point out that Willy and him devised ways to use rail wherein you can force trigger override networks that are in coded in the NAM but for practical reasons are limited in accessibility. I believe he showed the manual creation of a starter tile using multi-tile puzzle pieces and the bulldozer tool. Some pieces that were unstable would leave behind a rail stub that when dragged over with the RHW-tool would force trigger the RUL flag that enabled the override network.
This only worked, of course, because the NAM team had coded it so. If you remove the code, unfortunately auto-connect behavior still exists, but not much else.