I do shoulder edge ride on the interstate freeways (not illegal in my state because sometimes in rural areas its the only route available), so I do have some experience with that type of situation (just not in my own locality not in the area under discussion). So maybe I can shed some light on the issues involved.
Long story short, when it comes to bicycles on interstate freeways, that is the ultimate form of edge-riding, taking the lane when any traffic is present is not an option and you do not hold your line across freeway on/off-ramps but instead either:
----- Go part way down the off-ramp, stop and wait for a good break in traffic and then cross the ramp perpendicular and then continue on the freeway shoulder edge until the on-ramp, stop and wait for a good break in traffic and then cross the on-ramp perpendicular and follow the shoulder edge of the on-ramp up until it connects with the main freeway shoulder edge and continue on your way.
----- Just follow the shoulder edge of the off-ramp down or up to the under or over cross-street and cross over it going straight (stop sign or stop light) and follow the shoulder edge of the on-ramp up until it connects with the main freeway shoulder edge and continue on your way.
So long as you use that kind of submissive shoulder edge riding technique always yielding to ramp traffic and being careful how you deal with the over/under-pass on/off-ramps its actually a pretty safe way to ride. The biggest problem I've run into is narrow bridges without a shoulder edge. Narrow over-passes without a shoulder edge are usually easily handled by just using the second technique of going down the off-ramp and up the on-ramp shoulder edge but with bridges its a different story. This bridge is the one main headache I have on a 300 mile travel route I quite often take from where I live to Bozman, MT and back:
https://maps.google.com/maps?hl=en&l...=11,83.67,,0,0
That's a major freeway bridge going east out of Missoula that is narrow with no shoulder edge with freeway traffic doing at least 70-mph and usually more. The only way to handle that is to stop on the shoulder edge where the narrow bridge warning sign is and wait for a big long gap in traffic and then sprint across the bridge pedaling like a mad man to reach where there is once again a nice wide shoulder edge on the opposite side.
I don't have to deal with tunnels on the freeway up in my state but I imagine tunnels without a shoulder edge would be far worse.
Long story short, shoulder edge riding on a freeway can be done and done with reasonable safety by a cyclist. It's just that you practically have no road rights, or at least none that any other traffic has a chance in hell of respecting so you have to ride accordingly and stop and wait some times for a gap big enough to cross either an on/off-ramp or a narrow bridge.
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From the OP's description my best guess is that the cyclist in question tried to hold his line across the ramp expecting high speed vehicle ramp traffic to yield to him rather then waiting for a good gap to cross the ramp. Just a WAG on what might have happened based on my experience with riding a cycle on the shoulder edge of freeways.
Would the OP mind posting a google-map link to the road area where this occurred similar to the link I provided for that freeway bridge I find a real PITA to cross?