I just had an interesting thought cross my mind...

Currently on a trip where they paid full-fare J for me ($11k r/t, painful!) - on my way back from LHR-YYZ, that segment alone was $3,700. Can I get them (at the airport, LHR) to downgrade me to M, use a cert, and then get an MCO for the $2,700? Or would they have to refund fare difference to the travel agency.

Anyone ever done this? I'd prefer to salvage some of the value for myself

Not an answer to your question but a comment.

Not sure where you were going and if this could have been a possibility but for $11,000 you can get a First Class RTW ticket = a much better value for $11,000 plus the extra points.

I believe a Business Class RTW is about $7,800.

Without commenting on the obvious fraud aspects of this proposition, if you have paid with a corp TA, odds are they would be under direction to send it back there, which is the case for me. The only way to find out would be to try at an airport ticket office. However, if your ticket cost $11k and was full J, odds are that:
- C is sold out
- I is almost certainly gone

As to the RTW suggestion, that's great, but often times business trips don't allow time for all the req'd stopovers.

Whoa that's heavy to throw around! Who is being defrauded by this potential scenario? As far as I see it, I'm getting the service they paid for, and capturing the savings (which they had/would happily spend) for my own use. I do this all the time, get people to donate 50%-70% of J fare (so they save money too) to my organization (I work for a charity) and then use points or SWUs to get there much more cheaply.

Actually neither of those are true, but it was booked within 7 days, so the C fare didn't apply. J is ~$3500 each way to LHR and then another $4k r/t to the Middle East destination beyond that (same distance, much better service, half the r/t price...)

Yes exactly - I would have DEFINITELY done much much more with $11k than what they did... I never let travel $ go to waste like that... I'd never survive at a big company paying J for all my tickets

I tried to have them re-route my return differently to save at least $2,000 but the TA couldn't see the flights on her computer that Expedia and KVS see fine. ugh!

It actually is fraud-like, or at least irregular accounting. If a company (or charity) claims a deduction or a business expense of $11k and it is not used as intended, the balance sheet should reflect the residual balance. For example, if the company bought you a car to do your job, and you sold it, and took the bus instead, is that legitimate? The high-integrity solution would be to book a new seat in M/U, upgrade it, and refund the other to the payer. I work for a public company, and am entitled to fly paid J most of the time, but as a business person, I prefer to use all these SWU certs wherever possible to improve my company's bottom line.

Ticket refund is always to original form of payment.

You are far too generous. It is fraud and, in most companies, would result in dismissal or a severe reprimand on file.