Here it is. Scroll down the page to "File Extensions"

BAS    
BASIC file. A file containing a Basic program. It can be run by loading it into IS-BASIC. The Enterprise does not store BASIC programs as text but in a coded (tokenised) format.

WP
The file format for Enterprise Word Processor documents. Files written in WP (and saved by the SAVE command) should be named with the WP extension.

You found a big deficiency!
I looked arround but not found specifications for these files! Only partial informations available in diferent documentations and books but not a complete specifications 
I will try to make it!