"JP1 files" are for the program RemoteMaster (sometimes called RMDU) supported in the JP1 forum [Link: hifi-remote.com] . Using a current version of RemoteMaster (2.12.*) try to load the file, then to make a Girr (Girr is the native format of IrScrutinizer) thruogh File -> Export as Girr or IrScope file. Then import the generated *.girr file in IrScrutinizer.

If that does not work, please post [a link to] the file.