I actually had a relationship with another T in the office my T rented from; my T and I both travelled from opposite, large distances and this was the other T's home office (we actually used her literal office for our sessions) but when my T would go away (and she went away for an average of 3-5 weeks at a time) she'd ask me did I want to call this other T as my backup but I never would :-)

It is hard enough to talk to one's own T much less explain "everything" to a different, strange T, especially during a crisis of some sort?