Pick out the schedule you want in business class on Untied metal (partner only if it has available award space) and regardless of current pricing, an agent should be able to put you on it. Ask nicely and be specific.

The other day, I was flying LAX-ORD-PIT and LAX-ORD cancelled.

I researched options and asked to be put on LAX-EWR-PIT (upgraded with PlusPoints) even though LAX-EWR was Y0, O0, J1. Agent + supervisor conferred and put me in J via Newark. Your case is even easier since you did not "upgrade" but booked directly into business (with points).

If the first agent denies you (it does happen), don't argue. Hang up and call again. Don't ever agree to anything less than being placed back in business class for your transatlantic flight.