douglas said:"The dominant empire doesn't get any techs at all, previously researched or new development."
Like Douglas said, you get no tech. It was the case, many patches before SE4 Gold, because I managed to force Subjugation on a Neutral AI once. So that's what you may be remembering.
But that was removed, I suspect because it was too unbalancing on multiplayer - it is, in effect, automatic tech sharing without even the couple turns of diplomacy delay.
When I wrote the entry in the Encyclopedia Malfadorica
{clicky}, I didn't mention the tech transfer, because it no longer applies.