So while the story isn't the same as it has always been, your statement of "it has nothing to do with the network" is the complete opposite of what is true.
SVDO allows the setup of 2 simultaneous steams from the phone. It was chipset dependent.
I'm just a bystander without a dog in this fight

but my curiosity was piqued, so I did some Googling, and it appears that NKT is correct: SVDO is a new phone chipset feature available in more recent Qualcomm CDMA2K 'sets that has nothing to do with the network! So no additional network support or upgrades are needed for SVDO handsets to support simultaneous voice + data usage on a given network.
This surprised me because I did remember, back when Verizon first started rolling out EVDO services, reading about EVDO (with the "DO" standing for "Data Only") and it being compared to the forthcoming EVDV ("DV" == "Data+Voice") standard which was going to allow for a circuit-switched voice channel and packet-switched data channel to both operate simultaneously within a single "EV" session. EVDV was never deployed by any of the U.S. IS-95/CDMA2K carriers, and in fact I've not read anything that suggests it ever got off the ground, period.
From what I've been reading about SVDO, though, it sounds like kind of a hack.
The reason that non-SVDO chipsets cannot do data and voice simultaneously is because the entire 1.25MHz "channel" has to be wholly owned by either the CDMA 1x voice session, or the EVDO data session. They can't share or partition the session in any way, a problem that EVDV would have solved by introducing a voice component to the new "3G" version of CDMA2000. Instead, because EVDO is "Data Only," voice calls get handled by the same 2G service that handled voice before (1xRTT), and then when you want to use data, your phone baseband has to "train up" to 3G service (EVDO). (I am still unclear about whether perhaps the old CDMA2K 1xRTT "2G" data service could operate simultaneously on the same carrier with a 1xRTT voice session. If so, then it is rather amusing that where "2G" GSM [EDGE] did not allow simultaneous voice and data usage only to have "3G" GSM [UMTS/WCDMA] solve that problem, CDMA2K went in the opposite direction and LOST the same feature that GSM gained, and which CDMA once had...).
Without either EVDV or something akin to the aforementioned VoRA (packetized voice; like VoIP but without the "IP" part, heh), the CDMA2000 standard by itself cannot solve this problem. There is nothing in the standard that allows 2G voice and 3G data to share the same carrier.
So how does SVDO work? Well, it seems that what clever Qualcomm has done in their latest chipsets is to include
two complete RF chains! Meaning: two separate radio transmitters and two separate receivers that operate independently of each other. So if you are doing just voice, or just data, you are only using one radio. But if you do voice + data at the same time, you are actually using two separate radio transmitters in your phone simultaneously!
...which is what I meant when I said that SVDO sounds kind of like a hack. I could be wrong and they may have done an incredible job making this work efficiently (at the very least, I'm sure they managed to get both RF chains on a single chip die, otherwise SVDO would also be a nightmare for handset manufacturers to engineer around if they have tight space requirements, like Apple surely would in a CDMA version of the iPhone), but it sounds to me like a voice + data session on an SVDO handset is going to be a battery's worst nightmare, whereas I'm pretty sure that on a UMTS/HSPA handset, the baseband doesn't have to work any harder than normal whether you use one service, or the other, or both at the same time.
(For those in the know: do SVDO handsets have two distinct ESNs, one per radio? So a single SVDO phone would appear to the cellular network as TWO distinct devices? If not, then how would SVDO not at least require a minor software upgrade on the carrier's equipment to work properly?)
-- Nathan