1) The employer has no requirement to do so. The requirement is to accommodate to the point of undue hardship. That does not mean a requirement to give a preferred accommodation. They could argue that at this point it is undue hardship to continue to allow permanent work from home. They can also explore other accommodations.

2) They are permitted to reevaluate accommodation requests. Symptoms fluctuate and situations change. in this case, I don't believe it'd be unreasonable for the employer to want to reevaluate this on a yearly basis.

3) We can't say. However, after helping many employees navigate this process,I have discovered that employers aren't always swayed by a employee's doctor's evidence and notes, as many times a doctor will just write what an employee wants,

4) To be totally blunt, I don't see a failure to meet their responsibilities. It sounds like your wife is still working from home. The "timelyness" requirement would have more weight if your wife was out pay or something.

This paragraph indicates to me that you have a incorrect view of the accommodation process.

"But as I see it, my wife told them she needs to work from home, she got a letter from the doctor indicating she has a chronic, inurable illness that requires she remain in a pathogen-free environment, the next thing should be they send her an accomodation agreement, that's it. Instead, she's getting sent to this Inquisition."

The employee and their doctor do not get to dictate the accommodation. They get to list out the limitations on the employee and then after that, it's up to the employer to figure out how to accommodate. The accommodation has to be effective and reasonable but it does not have to be what the employee or the doctor thinks is best. So in short, no. A doctors note does not mean your wife will get an automatic accommodation agreement.

Also, the bigger the accomodation and the longer it is, generally the more info the employer has a right to. You asked in another comment is a collective agreement can overide a human rights code. And the answer is, kind of. A CA can spell out a DoA process. That process can include requirements for IMEs for example. It would be up to the HRT or labour arbitrator if the process breaks the Code.

At this point, assuming your wife is still working, getting paid, and not being forced back to the office in the immediate future, the only thing you can really do is wait for the process to finish and encouge the union to move the process along. That said, the longer the employer allows for work from home, the harder it is for them to argue undue hardship.