The article is in the Hidden Value column on the blog, the April 28, 2010 entry titled Intercepting PCL to Extend 3000 Printing. The article talks about several ways to deal with PCL generated on an HP 3000 system. RPM is listed as the reasonable cost option, though I didn't investigate the last item in their list thoroughly.
If you work with HP 3000 systems and MPE, you probably already know about this blog; if not, check it out.
The article seems to refer to RPM Select, which will, of course, do exactly what they say: intercept the PCL, then use a 3rd party utility on the data. RPM Elite goes one step farther by converting PCL to PDF. We have worked with customers who then take the PDF and send it to a non-PCL printer; we'll post an article on that shortly.
PCL is a pretty great format in that you can print it on roughly half the printers on earth, and it's not hard to find software that understands it. Once you translate PCL to PDF, you certainly open up more possibilities on how your end users can view the data–without printing.
By the way here's an article on how to set up your HP 3000 system to print to RPM.