Hello,
For the Rising Stars of Manga competition I know that they do send mass email rejections. However for general submissions, it states very clearly that if they are not interested they will not contact you---you are also not to ask them about the status of your sub. Basically, they function like most publishers out there.
Most subs focus on pitching a 3-volume manga series which means writers have to team up with a competent artist to provide samples to the company to consider.
Recently I did mail in a fiction submission (for a novel) and followed all the guidelines. I included a self-addressed stamped postcard which would confirm that they received the package but I haven't received the card either---so I know they didn't open the package yet. It's only been 2 weeks so I wont' start whining until it's been 2 months (^_^).
Example of someone who did receive a rejection:
"About two to three months ago I've mailed my manga in to Tokyopop inc. (the California office) but haven't recieved any reply. When I sent a previous pilot volume during the summer the people in charge of reviewing submissions sent a reply of decline, with in two weeks I've sent it."
Source:
http://messageboard.tokyopop.com/forums/showthread.php?p=322061#post322061
Overall, Tokyopop is considered by many to be a strong company with an international reach, and because they are the top of their field (in the USA) they are never in desperate need for subs. The talent comes to them.
Some of their original English language stuff is not consistently good though and there are only a handful of "hits" in the OEL category.
I recomment you join the TP forum and do some searches before posting questions.