Haha...they don't make RK together. The RK tractors are nearly 100% direct ports of the T224, T264, T25, T394, T454 and T554. They use Yanmar engines, but Yanmar has nothing to do with the design or building of the tractor. TYM also makes the T754 for RK, but it uses a Deutz engine.
This deal will have Yanmar effectively offering versions of some of those same tractors with Yanmar paint and stickers.
It is true that Yanmar and TYM have had a long business relationship...mostly it was just TYM buying Yanmar engines. JD had Yanmar completely make units with green paint and still uses Yanmar engines, too. The news in this deal is that Yanmar is going to be selling tractors produced by TYM.