Can a Mage be Both Communion Slave *and* Master?

[Yrkoon]

Jazzepi said:
If your combat order looks like this

SLAVE A
SLAVE B
MASTER C
SLAVE D

Then slave A/B will be able to freely cast spells each round. Master C will then cast a spell. And slave D will sit around soaking up fatigue and looking stupid.

If A and/or B cast spells in a turn, do they still count as communion slaves, i.e. are the paths of C boosted, and do A and B take fatigue from C casting spells ? Or are they out of the communion for that turn?