Insiders would have to declare their purchases even if it was only 1 share. I think you're thinking of entities that aren't insiders that purchase shares and yes, they would only have to report if they own more than 10% or so.
Inco/Vales interest is the later (I think). I wonder when they would jump in and increase their interest...I never really understood their holdings. Perhaps at one point Inco had a business model built around having an interest in small exploration plays like this. Vale probably loses this in their balance sheet and never pays attention to it. Surprised they wouldn't just try to get rid of these minor holdings just so that they wouldn't have to deal with them.
On the other hand, perhaps VIOR should have approached them to finance the drilling rather than bring in Norvista...I guess that's water under the bridge. Maybe some day Vale will come in and buy out VIOR at $10 a share!!!