Chinese telephone companies.

I left a comment over that The Register that got a little out of control. If anyone wants to hire a telco analyst, I am available.

In the mid 1990s, there were two 2G GSM mobile networks set up in China, one by the incumbent operator China Telecom, and one by a new company China Unicom. (We say "new company", but all these things were and generally still are state owned).
In 1999, the mobile assets of China Telecom were split off to found China Mobile. The advantages of being part of the incumbent fixed line operator up to that point were such that China Mobile was by far the market leader by then, a position it retains to this day. (China Mobile is by far the biggest mobile operator in the world). At the same time, more assets of China Telecom were spun off as China Netcom to build high speed internet infrastructure in China - i.e. to be a large ISP.
On order to supposedly compete with fixed line services, China Unicom was also given a Wireless Local Loop (WLL) licence. For this, it used the IS-95 CDMA technology developed by Qualcomm in the US, which was being sold as a WLL solution at that time as well as being a fully featured cellular system (as used by Verizon and Sprint in the US). China Unicom were highly aware of this, and thus used the WLL licence to build a second mobile network.

Meanwhile, the Chinese had decided that they did not want to pay huge levels of royalties to western companies to operate 3G mobile phone services, and decided that they would develop an "indigenous" 3G standard called TS-SCDMA to be used in China. (In actual fact, this was originally developed by Siemens to be possibly used as the European 3G standard, but this lost out to W-CDMA). While this was being further developed and made ready for use in China, no 3G licences were issued for use in China.
Thus, approaching the 2008 Olympics, there were no 3G services in China, and the Chinese were concerned that China Mobile was too dominant, and they were concerned that their "indigenous" 3G solution had not been launched yet, and they were embarrassed by the prospect of foreigners coming to the games and discovering that there was no 3G service, and they retrospectively decided that what was better was to have a number of telcos competing on both wireless and fixed line services rather than separating by function.

Thus the industry was reorganised:

China Mobile was awarded a TD-SCDMA licence, and ordered to roll it out at once.

China Unicom was given a W-CDMA licence compatible with the rest of the world, and was forced to buy China Netcom so as to offer fixed line and wired ISP services. China Unicom was forced to sell its IS-95/CDMA network to China Telecom.

China Telecom was instructed to buy China Unicom's said IS-95/CDMA network, and upgrade it to 3G speeds. (China Unicom had already done this to some extent).

Thus we have three mobile networks, the biggest of which has 2G GSM and a strange, 3G network using a standard used nowhere else that few people use and which doesn't work very well, but which has most of the customers. (There is no number portability in China, so customers don't often switch network). The second largest, China Unicom, has the combination of GSM and UMTS/W-CDMA that most iPhones are designed for, and that is why they have been the only network offering the iPhone until now. (Apparently several million people use unlocked iPhones on China Mobile's 2G GSM network in EDGE mode only).
And you have a third mobile network, which uses CDMA/IS-95 as used by Verizon in the US. Apple's introduction of a phone for Verizon earlier this year didn't quite solve the problem, though, as the use of a SIM is optional on CDMA, and China Mobile uses a SIM and Verizon doesn't, and the CDMA iPhone 4 does not accept one. Hence we have had to wait a little while for that problem to be ironed out. My assumption is that the new iPhone(s) that we will see later this year will solve that problem.
China Mobile is going to use 3GPP LTE for 4G phones, as apparently are everyone else in China. At that point all three carriers in China will probably carry the iPhone, but we won't see that until late next year at the earliest.