On my 1-st escort mission I've seen a cyborg with a two M16 rifles. I've train one of my solders with a some training, that gives me an ability to wear two weapons simultaneously, but I can't use two rifles Can I?

You cannot double wield rifles. Only pistols and SMGs. The folks you escort tend to have a few exceptions to the rule, I find.

Still, a really toughened up cyborg ranger with a pair of SMGs can become more than a match for someone with a heavy machinegun - so don't let the fact it won't let you do the same with the rifles deter you from continuing down that path.

- NKF

If I recall correctly, There is an M4 variant in the game (looks like an M16) that Cyborgs can eqip as a single hand weapon, but all other types of carracters must use it as a 2 hand weapon. I may be wrong. My memory is a bit fuzzuy about this as I havn't played it in a long time now.

This is not M16, or M4 ... this is Colt SMG. It's looks like M16 series rifles but uses 9mm ammo. If you want more information of this design look here.