A bit of testing shows me that apparently BW will not automatically load chapter notes with an .RTF extension; and I don't think you can make the notes editor default to that extension either. On the other hand, BW's files that have the .BWW extension are in fact Rich Text Format files, just with a different extension name. I find that if I just change the extension name of one of them from .BWW to .RTF, it opens fine in, for instance, WordPad.
If you use the Save File As function in BibleWorks to save .BWW files as .RTF, you can create .BWW notes files and save them as .RTF files, which should open on your Android device, in whatever app is set up to work with them. It is a shame that Android doesn't let you assign file types and extensions to apps, though.