I am a bit confused about how the reforms work in 0.8.

I just had a Polybian reform. For a very long time I had no new units at all, then suddenly one of my cities could recruit the new units (I had a tier 5 MIC). Another city with a tier 5 MIC could still only recruit the old units.

After looking a bit more closerly I found a tier 5 MIC in the builing options of the second city. Upon inspecting this builing, I saw that this would recruit the new units ...

So my question is: Do the old MICs need to be replaced to get the new units?

Also, if we don't replace the old MICs does that mean we can continue producing the old units?

Finally, a slightly unrelated question, but why are Samnite troops no longer available after the Polybian reforms?