The difference in colorfastness may also depend on the type of ink used by the printer. Water-based inks, for example, are less colorfast than pigment-based inks. This website is about paper, but does explain some of the differences in inks used by different printers:
http://www.printindustry.com/Newslet...etter-135.aspx
I found this website that explains how to create your own fabric sheets. I think it uses the Bubble Jet Set; however, there is a side bar link on how to create your own colorfast setting solution (which mentions that the fabric softener route is not as permanent as others):
http://www.ehow.com/how_6374690_make...jet-print.html