Polity and tradition
For the record: I've had critters in my church before, too! (for Blessing of the Animals, on the feast of St. Francis of Assisi-- the weather outside was icky).
On the other issues being bandied about, however...
Let me state first that I don't believe that this has anything to do with the Roman Catholic Church's dogmatic opposition to women's ordination. It's not about a woman priest serving, but rather about someone other than an ordained RC priest (or deacon--also canonical in RC tradition, as it is in Anglicanism, I believe?) formally proclaiming the gospel in the context of the Eucharist, in opposition to canon law and tradition. The same restrictions apply in the Episcopal Church (though there are rare variations-- allowing a layperson to translate the gospel for a congregation that does not speak the same language as a visiting priest, for example, is certainly permitted). One may disagree with the rubric; but that's the way things currently stand. Fr. Martin would not be reading the Gospel in my church either, even if he were a guest preacher.
I would imagine there would not have been an issue had the Episcopal priest been invited to take another role, or even to read another of the scriptures of the day (as any person may do, with the consent of the clergy). There is certainly precedent for this. I have attended many RC masses over the years with people taking on a variety of roles. I've even been invited to participate in a few myself, before as well as after my ordination, though my role has always been within the confines of rubric and canon.
As to Communion: It is our current faith practice in the Episcopal Church that any person may come forward to ask for a blessing, and that any baptized Christian may receive the bread and wine. Yes, this distinction is a hot topic in theological circles, and there are any number of theologians far more learned than I who debate this particular stance, with many who argue for fully open Communion; but again, that's where we are today.
That said, I do not make a practice of inquisition at the rail, and I don't know of any decent priest who does. If someone I do not know comes forward to receive, I will err on the side of offering the sacrament without a qualm. However, if I know someone is not baptized, I will offer them a blessing. It is also not unusual for a Christian to ask for a blessing rather than the sacrament, for reasons of their own (honoring restrictions in their own faith tradition, for example, or personal concern about the current state of their souls). In either case, I am as careful as I can be to offer God's blessing in a way that does not seem in any way to relegate the receiver to second-class status. All people are welcome and encouraged to seek God's grace. Period. No, it is not the same thing; but the altar rail during worship is not the time or place for theological discussion or dispute.
So it seems to me that both priests might have followed a similar practice, had they chosen to do so, without giving or taking offense. I could wish things were different, of course; but were I in the Episcopal priest's position, taking another liturgical role, and accepting God's blessing from a friend and colleague in ministry would certainly be acceptable alternatives.