Well, of course they do. Its not like you INSTANTLY become a mindslave...
However, its effect is instant. Not powerful, but instant. At the start, the change takes place immediately, but its so small that its likely to be overlooked. After about a week, you'll have minor discontent among the average citizens, and the weakest willed completely taken by the Mechera's way(mind, thats the weakest of willed, so its not much). After two weeks, many people would protest the current government, andminor riots would occur, maybe even a small rebellion. Into week three, the majority of the population is under Mechera dominence, and they'll overthrow the government in the name of the Mechera. Thats Propaganda Hub. The Media Hub is both instant and powerful, but it only affects targets already subjugated to Mechera rule by the Propaganda Hub, and so it isn't usable until the Mechera have won anyway.
And Orph, technically thats plausible to happen. Not exactly the same, I'll admit, but its plausible for such a technology to be discovered by another empire. So long as is sufficently different, there's no reason that couldn't happen...