I don't see how they could. How large are the technocrats in Manchuria? From what it has sounded like so far, it is mostly a fringe political party that only exists due to Chinese influence. If that's the case, then I don't see Manchuria really going so far as to secede, even if a referendum is offered. And I don't see the Chinese even going so far to allow one. If they do, and it fails (which it likely will; Manchurians may not be fond of Russia, but they are farthest from the homeland and have one of the largest populations. That probably makes them one of the more influential members of the IEF.
If secession happens, then they will likely fall further and further into the Chinese orbit. And as it is, the devil they know is bad, but the devil they don't is likely to be worse. (The Technocrats do seem to be a big boogeyman here) So, any referendum will likely see them remain in the IEF. ...That's why I think the Technocrats won't allow it. Wait for a response from the Motherland Government about how they will not allow a referendum, use that as a casus belli to "liberate" Manchuria and properly reintegrate it... Oh, and while they're at war, take the time to reintegrate the remainder of China which had been forcefully torn away a century or so prior. If the Technocrats go along with a referendum and they lose, they forfeit the ability to claim the mantle of liberators.
And, if the IEF is losing the Far East, I don't see how they refrain from going nuclear. If they don't, they lose horribly and all of Asia from the Caspian to the Pacific becomes a Technocrat playground. And I think they still have more warheads, anyway, if I remember correctly.
I'll cover the technocrats in Manchuria in greater detail soon but they are more than a fringe element. Granted if an election was held they wouldn't win a majority but due to their Chinese/Korean backers they are easily the most effective pro-independence organization. That gives them a level of credibility with the masses.