Thanks a heap!

If my LAX-EWR-BCN flight clears on the LAX-EWR leg but not BCN, then I'm entitled to a redeposit? Previously in the same situation I wouldn't have?

yes but experience for many is the clearing of the PS flight is far from certain.

This has been inconsistent / ambiguous. There have many a lack of clarity. Given the difficult of clearing the combo PS / Intl has not had many cases reported. The PS/Domestic case has been tested and reported a few times and the results had been mixed.
Now it is clear (no refund of the domestic segment clears but the PS does not)

Yeah, I think the only reports we could get were that sufficiently motivated FTers could get an agent to read the rule in whichever way happened to benefit them the most in their present situation.

A friend has some expiring GPUs, and I am on a flight with R9. My fare class though is L, so can't upgrade. What's the process to upfare - do I call in and ask what the difference is (and then decide whether it's worth it)? Do I pay just the fare difference or is there a change fee (I'm plat).

Call and say you would like to upfare to a fare that will allow you to apply a GPU. I would run a search right now to see what that fare is (likely a W) and how much it will cost.

There's a wide range of experiences whether they will waive the change fee. You could try referencing GG BUYUP.

Thanks - looked like maybe a V fare - a little hard to determine because it's one direction on roundtrip.

Just to reword it since UA now calls PremiumService just Business, there is no refund if I clear LAX-EWR but not BCN?

UA has removed the previous uncertainty, a PS segment does not consume the GPU if the Polaris segment does not clear. It would be refunded.

On the contrary, if you clear LAX-EWR and not EWR-BCN, you should receive a refund because LAX-EWR is not an international Polaris flight.

I'm booked phx-ewr-LHR on 12/18 confirmed in Polaris using a GPU. 24 hours out if I look at my SDC options will they show confirmed Polaris options if available? I'd much prefer to get on the lax-LHR flight if possible.

SDC will not show options that involve clearing R space and upgrade is not automatic carried over in SDC.

Strictly speaking you will have to SDC based on your purchased fare and then if R>0, apply your instrument. So you will have to manually search if the desired segment has R>0.

Once your have a cleared upgrade segment, your will have to use an agent for SDC. But it is not too difficult, like cfischer , I have SDC a couple times to flights with R space.

Good info thanks. Right now UA 108 on Sunday lax-Lhr is showing R7. Is that what I'm looking for t-24?

And your original fare class (W?) will need to be available on PHX-LAX-LHR.