The ECC88 is a 6DJ8 and the E88CC is a 6922. I can't say for sure that the JJ's are being true to the original specs, but a 6DJ8 and 6922 are slightly different. That said, but amps are using JJ's. Not a lot of choice, if you don't want to source NOS tubes.
It's interesting, if you look at the page I linked to at the JJ website the tube is listed as "E88CC - 6922, 6DJ8", if you click on the More>> link at the top of that document it says "ECC88" ... so it seems they're positioning their tube (perhaps incorrectly?) as a replacement for all the above. http://www.jj-electronic.com/pdf/E88CC.pdf
The entry in Wikipedia for the 6DJ8 says:
"Although not originally designed for the purpose, it became popular in hi-fi audio amplifiers. European-produced version of the tube is designated ECC88. An industrial (improved/higher ratings) version of the tube is designated 6922."
Edited by USAudio - 4/25/11 at 10:15pm