IIRC the Burley used set screws working against the eccentric to hold it in place. (Sometimes the outer surface of the eccentric gets embedded by the screws and won't allow fine adjustments, filing down the contact area of the eccentric held fix this.) The usual problem is that the BB is frozen into the eccentric, not the eccentric being frozen in the shell. Is either of these going on? My Duet was the first generation and had cartridge bearings front and rear. In 15 years of use I only replaced them once, and not because they needed it. In hind sight I should have left them as was. The removal and reinstall went OK but was a pain. Lots of care to measure the axle extensions beyond the bearings outer edges to insure the same chainline after installation. LockTite to hold all in place. Done in steps so the axle didn't shift along the axle. (One bearing Locktited to the axle, the other into the shell as the first step.) Not sure how this second generation of Burley tandems were done. If you have the large cartridge bearing and they spin well/smoothly the most i would do is to pull the outer seals and flush then re grease the insides/bearings. The insides of the frame can be drained/dried out and not remove the rear bearings. If needed extra vent holes could be drilled in the stays. If the eccentric is stuck in the shell then you need to free it up. Removing the set screws and dripping in some ATF (watch the paint!) will help free it up. But in the end brute force is the usual method. Take care to isolate the bearings and the eccentric's outer edge from impact damage.

Maybe someone with more current experience will chime in. Andy.