There are a couple of reasons, why I think you are right. First of all I believe consumers will not suffer in any way, **PROVIDED** Telecom does not change the terms it just proposed:
1. they will NOT disconnect you while you are on
2. there will be no prioritization which could not be done even without the new prefix, because emergency calls already have the ability to kick out other calls to get through (so on that point they are already trying to bullshit the people), and Telecom could as easily prioritize the existing ISP number as it could the new one (just makes it a bit easier for them)
3. AFAIK, there are no lower quality lines they could route data calls through, they don't have some old shoddy lines they could use for data, it is all the same stuff
4. service could be degraded if they route you with lots of detours, BUT that makes it only more expensive for them, so no danger here

So with no harm to internet users that I can see, your explanation is the only thing that makes sense to me.

-- I don't work for Telecom either, in fact I don't work for anybody but myself! ;)