Hey folks, I think I spoke too soon with my response 14 days ago. I misunderstood and assumed the id_token was available. There is a token on the reconcile lambda, but it is the access_token, not the id_token. My apologies.
That said, there is some work happening on issue 323 that you probably want to track: https://github.com/FusionAuth/fusionauth-issues/issues/323 (a comment or two way at the bottom). It's not finished yet, but we're looking at ways to make the id_token available to the open id connect reconcile lambda.