I'm flying Vancouver-LAX-Sydney later this year with Delta, then VA on LAX-SYD leg.

I'm flying Vancouver-LAX-Sydney later this year with Delta, then VA on LAX-SYD leg. I know my bags should be checked all the way through to Sydney when I check-in at Vancouver. But Delta arrives into T5, yet VA departs from TBIT. Does this mean I have to exit through customs/immigration or is there an airside bus shuttle that will take me to TBIT?

This website won't let me paste it, but there is a 15 mins walk, or a 5 mins bus from a Delta flight to a Virgin flight at LAX.

If you are interested in reading it for yourself, google Virgin Australia Delta Airlines partnership.  Or tranferring from a Delta to a Virgin Australia flight at LAX.

Its very unlikely you will have to go through US Immi, but would probably have to clear transit security, ie, xray again.

It should come up under within the Virgin Australia website, that is where I found the info.

Ah, I now see the confustion.

Most countries if you are not entering, you don't have to go through immi, but that being the US, they probably make all and sundry do it.

Its not exactly clear, even after reading that website, if transit pax have to go through US Immi.

On that website, it says down the bottom, they have added together, arriving and transiting through Los Angeles Airport (LAX) .

Your bags will be checked through to SYD. Your boarding passes for all flights will be printed at Vancouver. Yes you will have to exit T5 and take shuttle bus to TBIT. When you get to TBIT double check the boarding pass with VA. I have had it happen to me once before that I wasnt 'properly' checked in for the LAX-SYD sector. 

I did similar routing a few years ago albeit the YVR flight to LAX was a Virgin Australia interline ticket with Alaska Airlines. YVR is unusual as the terminal is split into USA flights and then everywhere else. It is the most bizaar experience as you not only do immigration clearance and customs for the USA in the YVR terminal but then walk through with a big "Welcome to the United States" sign before even boarding your flight.  Then you can just do a terminal transfer by bus or walk at LAX and yes you are treated like everyone else and need to go back through security and immigration to depart the USA.

You will need to do immigration but you are pre cleared at YVR.  All passengers traveling to the us from major canada airports are pre cleared which allows you to be treated as a domestic passenger on arrival. The U.S. does not allow passengers to transit.