The barcode writer currently only supports Australia Post FCC types
11, 59 & 62; i.e., the Reply Paid Barcode (FCC type 45) is missing.
According to the specifications (see
http://www.auspost.com.au/GAC_File_Metafile/0,,2043%255Ftechspec,00.pdf),
FCC type 45 is identical to FCC type 11 except for the different FCC
code (see p. 9).

So, it seems that to support FCC type 45 all that is needed is to add
a barlen for getinterval (45); i.e.,

    /barlen barcode length def
    barcode 0 2 getinterval (11) eq {37} if
    barcode 0 2 getinterval (45) eq {37} if <= add this line
    barcode 0 2 getinterval (59) eq {52} if
    barcode 0 2 getinterval (62) eq {67} if

Regards,
Stephan.

I've just committed your improvement as supplied and tagged a new release:

http://code.google.com/p/postscriptbarcode/source/diff?old=117&r=126&...

Thanks!

Tez