UPDATE 3: Looks like I was indeed correct. Ishiwaka Tsutsumu has an article up on the Nikkei. Skip to page 2 for the important part.
Because the only carrier will by SBM, the version on sale in Japan with be non-LTE.A paragraph later, this comes in. It's my understanding that "Softbank 4G" is using Willcom's XGP, which can be relatively easily converted to TD-LTE.
Based on the current situation, I don't think SBM can start LTE service anytime soon. So, it seems that LTE can't be used on the new iPad [in Japan]. So, if the iPad here will not be 4G, why call it 4G? I really wish people would stopped doing that. Call it what it is, please.It's unclear to me what the progress is on this, though. (Docomo, AU, AT&T, and Verizon are using FDD LTE. The same chipset can (apparently) support both.
UPDATE 2: Perhaps in the case of Japan, "4G" is referring to Willcom's XGP that is being converted over to TD-LTE?
This post has been updated. When the iPad was first released in Japan, Apple did a poor cut and paste job into the Japanese site that resulted in ambiguities regarding whether or not it was SIM locked to SBM's network. Without seeing specs that specifically say LTE, I would be personally leery of buying it. Remember, there were people who preordered Japanese iPads thinking they were totally "SIM Free" when they weren't.
Currently the Japanese JP apple site contains conflicting information. On the one hand, it uses term "4G". On the other, it lists specific protocols and frequencies, none of which are 4G. UMTS, HSPA, HSPA+, and DC-HSDPA are all 3G (or perhaps 3.5G). They certainly are not LTE. (See here for J carrier plans for LTE). Let's also not forget how marketing wonks like to abuse the term 4G.
Wi-Fi + 4Gモデル：UMTS/HSPA/HSPA+/DC-HSDPA（850、900、1,900、2,100 MHz）、GSM/EDGE（850、900、1,800、1,900 MHzNow, let's contrast this with the US page.
AT&T Model: LTE (700, 2100 MHz)
Verizon Model: LTE (700 MHz)
The US page also has an expanded description of 4G that specifically mentions LTE.
The Japanese site also has an expanded description of "4G" that doesn't specifically mention LTE. It mentions being able to use 3G protocols when 4G isn't available. Now, this would seem to indicate that there is LTE. Without clarification, I'd be hesitant to buy.
Original post below:
We have several LTE carriers here, but LTE is not listed in the specs on the JP apple site. The only carrier is Softbank.
Wi-Fi + 4Gモデル：UMTS/HSPA/HSPA+/DC-HSDPA（850、900、1,900、2,100 MHz）、GSM/EDGE（850、900、1,800、1,900 MHzThis will work with AT&T 3G network in the US.