No, the Romeo4 uses proprietary mounts. The CR2032 powered Romeo5 models are compatible with Aimpoint H1/T1 style mounts.
Yes it will work with H!/T1 mounts but the front of the sight will extend a little further than a regular T1 and it may look a little goofy, but it will work
I just bought a "Battle Steel" mount to use on my Zenith ZR5-S, MP5 clone. It is the one that will enable a co-witness with the Aimpoint H1/T1 micro red dot sights and also the Holosun optics. I attached my Sig Romeo 4m to the mount and it was an exact fit and does indeed provide a center co-witness with the BUIS. With this being the case, I would think that that the Romeo 4 series will work on an Aimpoint T2 mount. However, I have been wrong before.
Although it is a longer optic than a T1/T2, it will fit on T1/T2 mounts. It fits on my Unity Tactical FAST micro mount but overhangs on the front which is OK with me.
No, the Romeo4 family has proprietary mounts. The Romeo5 is compatible with T2 mounts.