I wanted to get the definitive answer, so I wrote ALPA contract enforcement this letter:

When you have a 2-leg dead head, say MEM-EWR then EWR-CDG, if you deviate on the first leg but plan to take the same flight as scheduled for the second leg, are you considered a deviator? There are a couple of areas of concern here. The first is protection if that leg happens to cancel for some reason. Does Crew Scheduling have the responsibility to protect you or rebuild your pairing? Second is are you eligible for the scheduled ground transportation?

Here’s the response:
Old/new CBA has the same language and intent .......You may deviate from
the initial leg, join the second, and you will be afforded the same
protections as if you had not deviated. Ground Transport will be
available as per-schedule.

I wrote this follow-up letter:
Thanks for the reply...could you supply the specific CBA
reference for this....not that I don't trust you, I would like to
have the reference available if necessary to convince *crew schedules
or duty officer.

Here’s the response:
There is no specific language in the CBA. It is just the way is done,
although from time to time there have been problems.

Oops. OK, I deviate on the FIRST LEG ONLY on my next pairing and the pairing ends up saying “services cancelled”.

Here’s what I wrote the union:
....not only are the services canceled, but I'm sure if there's a problem and I have to call crew scheduling they will look at this and go "you're deviating, sorry, can't help you". Absent specific CBA language, what am I supposed to say if I find myself in this predicament? On the other issue, I don't really care about the scheduled GT being canceled, although if you say the CBA is supposed to allow us to take the company provided transportation, I see this as bad precedent. But it would really bother me if I was on the same plane as someone who took the scheduled flight from MEM and not have the same protection as them. This problem becomes especially critical now that the company is routinely scheduling these pairings with 18 hours crew rest after the oceanic crossing, thereby eliminating much hope of a backup.

Here’s the union response:
I'll have them look at this. You are certainly protected and the GT
should not have been CX!

Contract enforcement evidently spoke with the company and it was determined that there was a “software problem” .O even mentioned it in an FCIF or lettter and said it would be fixed, but I don’t feel real good about getting any love from crew scheduling if I don’t make it in time for final check in. And by the way, scheduled ground transportation for my trip WASN’T there when I arrived.

GOOD LUCK.