Oh I see what you're saying. I couldn't find any Russians sources (yet), but then again....
-Russian news didn't immediately reveal S-300 deployment in 102nd baseeither.
-It did refute, for example, when Assad said that he received S-300s
Why would Armenian defense ministry lie? It's not like we're saying they are our missiles. There is no incentive to lie....
EDIT: Ill post Russian sources ASAP.
Just because the same news is posted on a Russian website doesn't exactly proves anything. The source of information is not Russia, and there is neither any further comment from Russian sources.
They would be still in Armenia despite belonging to Russian military, and that in itself can be regarded as a way of pressure on Azerbaijan, so yes there would be actually a "incentive" to do so.
I'm not completly ruling it out either, but in this situation the existence of them is not really confirmed.