in this post: https://support.google.com/dfp_premium/answer/1242718?hl=en (under Tracking Macros - Pass IDFA/AdID macro)
The IDFA/AdID is exposed in the adcall to DFP and they are now allowing
access to this using the macro
%%ADVERTISING_IDENTIFIER_PLAIN%%
Previously you would have needed to write code in the App to access this
and insert as a KeyValuePair in the adcall and then use the %%PATTERN%%
macro method to extract it out in the ad... So... a lot easier. :-)
So you could then pass this on to a 3rd party if required.
Cheers
Seán