Can my iPhone4 tethering give the iPad a GPS position?

Technically, yes (e.g. using the Maps app), although OzRunways works by “asking” the iPad for an accurate position. If the iPad deems the position inaccurate enough, it will not pass the position to the OzRunways app. It seems that the iPad sometimes does not trust the iPhone4′s position so it doesn’t always pass it on. Best to get a dedicated bluetooth GPS.