If I book a Premium Economy TATL ticket with miles, can I then upgrade to Polaris using Plus Points (I'm a 1K) ? The website talks about using Plus Points to upgrade paid economy and premium economy tickets, but not about tickets that you "purchased" with miles. ....
Unless you are a GS, award tickets can not be upgraded by PlusPoints.
There is a potential workaround. Economy award tickets can be cash upgraded. In that case, the ticket fare class is a paid fare class and it appears PlusPoints will work.