Dark Sol, it would be a "dark day in hell" before you would be inclined to push your bike 15 miles. I think, you are a bit like me, in that you worry to much about the 'what ifs'.
Not sure who would be the 'expert' on this one, I'll give you my opinion. I 'think' the gears (bearings) are lubricated from "the inside out". That is to say, with the engine running, and the bike in gear, the gears are meshed in such a way as to 'push' the oil "into" the pressure points. Without the engine running, the oil is not 'pushed' but a couple of the bigger gears may contact the oil, at least a bit and pull it up from the crankcase. In any event, without the engine running, and in neutral, not much oil will be getting to the bearings. Then again, if you are pushing, I don't think it be anywhere near the concern as it would be if you were being towed (higher speed/more heat?).
I don't think anyone would be inclined to push their bike very far, unless perhaps they were 18 and the Girlfriend called on the cell and said, " I really Love You and I think it would be REALLY SPECIAL if we took your bike to that neat area by the creek.
Well, that was my dream anyway . I would accept a tow for 5 miles, put the bike in 4th and hold in the clutch, then let it out from time to time to engauge the gears to pick-up oil. Please understand, this 'idea' comes from the gut, not any experience that had me tearing down an engine and double checking the result of my 'folly'. Lets hear what others have to say.... Gerry