I've ridden Lake Mary Road several times. I've personally never had any incidents using this highway, but it can be busy in the summer. It would be nice if it had more oxygen, though.
It's one lane in each direction, plus a shoulder in each direction, but they're not extremely wide shoulders. The grades are such that riders can get going downhill at 30+ mph as described in the article. At those speeds, trying to keep a group entirely on the shoulder could be risky. Arizona has no mandatory bike lane or shoulder use law (except for fully controlled access freeways), and a rider in the travel lane riding alongside another cyclist fully occupying the shoulder could arguably be determined to be "as far right as practicable" in accordance with
ARS 28-815.
From the video, the RV driver would seem to have exhibited at minimum simple negligence in failing to pass the bicyclists with sufficient space as defined in
ARS 28-735. From the article, it seems the driver may have been cited for 28-735 violations. Now the bad part: 28-735.C says the fines do "not apply to a bicyclist who is injured in a vehicular traffic lane when a designated bicycle lane or path is present and passable." So if the driver was cited solely under 28-735, there's a chance of no civil penalty at all. But other violations could be written, such as for
ARS 28-701.A (Basic Speed Rule). But all that is up to the Coconino County Sheriff's Office.
Arizona has no caps on damages in civil claims, so every injured or affected rider could possibly file tort claims against the driver for whatever amount they thought appropriate, including punitive damages for alleged reckless negligence. The video linked in the article could be an important piece of evidence in such litigation. But the defendant and its insurers could aggressively defend the case, claiming comparative negligence on the part of the bicyclists and hoping for a sympathetic jury.
Disclaimer: I am not an attorney and this is is not legal advice. I'm familiar with this roadway on both two and four wheels and have a working knowledge of traffic law in a professional engineering capacity.