Solido are part of the "Simba Dickie Gorup", along with Majorette, Schuco and Tamia (I think). So far I haven't seen any evidence of Norev being part of the same group or being affiliated with Solido. But I might be wrong.
I think this is more of a case of using old molds. I've already mentioned the models that are on sale and the ones that were announced here:
I own some of them as well as Solido's versions (some were actually Majorette originally), and I can say that the Solidos are a touch better. If you have the chance buy the Solido version, but if only the Norev is available it's still good, plus they offer some new colors.