Google search turns up nothing...surely some fans of this game have created their own scenarios over the years (25+ !) with the included scenario builder and shared them, but be buggered if I can find any. Does anyone have some info?

You're right: it's somehow weird that, even though it didn't sell that poorly, was shipped with a dedicated editor and tried to please quite a sizable community - the WH40k fans -, no fan-made scenarios were ever shared.
As someone who tackled with the editor (and the game's files) a lot, I suspect that this has to do with that editor's limitations: it was obviously shipped very hastily, much like many other aspects of the game - which were apparently changed at the last minute or, at least, even after the manual was printed. Regarding the editor, you can't (for example) access the specific menu you'd need to transform your scenario into a mission flagged for the campaign (like those narrated by Captain Kruger), which forces you to smuggle it differently (swapping the original missions with yours) and, even so, it doesn't work so well. Many bugs and weird issues will occur as soon as you start modifying files on your own; issues, I must add, which could have been easily avoided and only happen because of the way the game has been coded.
And even if you were only to stick to most safe procedures, developing a very basic scenario with simple elements - a few units, a few traps, an object to pick somewhere on a randomy generated map: done ! -, you'd still have to face problems dues to poorly documented features, such as the way (locked) doors and keys are handled tor example (with the scripts supposed to work... well... actually not working that well). And there are other similar troubles down the road...
So, in the end, I guess the few people who actually delved into that kind of work - you'll find people talking about that on old forums, from time to time - eventually gave up or (like me) kept their results for themselves. Because the sum of work required before you'd be able to offer something really enjoyable, stable and bug-free would seem quite impressive ^^'... I might, one day, end up polishing the things I did, but that's not for now I'm affraid.