I believe this is BDI's idea of a cross-over event, though I'm not actually familiar with any of the series the characters originate from. Unfortunately, there wasn't any indication that these are anything other than standalone specials in the original releases names, which likely prevented many who might be interested from following the story at the time, and explains why it's never been collected... 'til now! :)
Contains:
Cricket, Agent of UNICORN 01 (2012) (c2c-1920px) (Darkness-Empire)
http://bigdogink.com/store%23!/~/product/id%3D18684009
Rookie 01 (2012) (c2c-1920px) (Darkness-Empire)
http://bigdogink.com/store%23!/~/product/id%3D18684011
Electric Youth 01 (2012) (c2c-1920px) (Darkness-Empire)
http://bigdogink.com/store%23!/~/product/id%3D18684013
Slipstream 01 (2012) (Tarutaru-Novus-HD)