Sadly no, if an assassin has guards they will not accompany him in the assassination attempt. They will, however, attack the province in a revenge attempt if the assassin leader gets himself killed. I guess that's why they're "not yet fully-trained assassins."
-Max
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Bauchelain - "Qwik Ben iz uzin wallhax! HAX!"
Quick Ben - "lol pwned"
["Memories of Ice", by Steven Erikson. Retranslated into l33t.]