Seems like you ought to be able to do something like piping your command through tr to change the delimiter character to a newline and sending it into a file, then using osascript to tell OmniOutliner to open that file.
A rough example:
Code:
df | tr '\r' '\n' > /tmp/foobar.txt ; osascript -e 'tell application "OmniOutliner Professional" to open "tmp:foobar.txt"'
In this example, it isn't necessary to use tr, of course, but pretend that it was sticking a '\r' at the end of each line as the delimiter. You didn't actually say that you wanted the document opened on the spot, but that's how you would do it. Note that you have to use the old-style Mac file path syntax, not the Unix variety -- don't repeat my earlier mistake! This could all be bundled up into a shell script if you plan on doing such things frequently.