So here's an update on the situation.
Today, April 27, the
revised formulary is finally published on the website, the very day it goes into effect. The
letter likewise shows up. I notice that the language promising the 60-day notice period for formulary changes is mysteriously missing.

I wish to G_d I'd saved a screenshot of that. It's 1984 all over again: "but we've
always been at war with Eastasia! You must be misrembering, Citizen." You shouldn't be allowed to edit history in real life. G_d damn it.
(And it really is in effect: we're getting rejects on stuff that's been covered since forever.)
As far as the Mebendazole thing: Hanlon's Razor states, "Never attribute to malice what can be adequately explained by stupidity." However, in this case, I really do sense malice. How so? Well, I called a СѴЅ nearby and asked whether they had mebendazole in stock. Of course they did; he seemed surprised that I would even doubt whether they have such a common item.
Now who administers the pharmacy benefit for Fidelis? СѴЅ/Сагемагк, of course.
They can't restrict you from going to any pharmacy you want; Aide of Right tried that when they bought PCS and there was a
huge backlash. So what did they do? They must have bought up the entire last production, squirreled it away in their warehouse, and cornered the market, so anyone with a prescription for mebendazole
has to go to them for it.
(How do I know they did this? I was there when they did it the first time. Remember when the old generic albuterol inhalers were pulled off the market because they had R12 as the propellant? СѴЅ bought up the entire last production run from Apothecon, cornered the market, and then had us take them out of the boxes and dispense them in 60-dram vials. What was the point of wasting money like that, I hear someone ask? Because the box bore a notice that the product was immanently being discontinued, and they didn't want their customers to know. Then of course Сагемагк wouldn't pay for brand name Proventil/Ventolin/Proair HFA, which were the only ones still in production with R134a ("HFA") propellant; no, they only paid for the generic albuterol, which was only available . . . guess where.)
They did the same thing when Apotex brought out the generic Plavix and was forced to pull it shortly thereafter. It's nothing but a backhanded way of ensuring a captive customer base. Illegal? Probably not. Unethical, or just sharp business practise? I think I'll abstain on that one.
Naturally, when СѴЅ bought Сагемагк, they swore on a stack of dictionaries that they would keep the PBM and the pharmacy separate, and deal with СѴЅ stores just like any others.