Just did it. And man am I peased with the results!
I've always been disappointed in how dark Tamiya OD is, and how light MM Acrylic OD is. So I blended the two in an old MM Acryl OD bottle 1/1 ratio, and I finally got the shade of OD I've been looking for! And the paints blended just fine.
Performed the test on some diorama accessories I've been painting lately.