But now I have made a great discovery! Well, I think so, at least.
To say things short: while playing TOB with an evil party, my cleric was Viconia. I don't like her at all, but evil is evil. In one fight, an Imprisonement spell was cast on her. She was lvl 31 then. And because I don't like her, I was not concerned - Edwin had the counter-spell for that (whatever its name is in english, I don't know, I'm playing in my native), so I rested and got him to cast it. She appeared, with all her things, just like she disappeared - I talked to her and joined her back in. And that very moment, I got a message like:
Viconia - your deity has rewarded you with its holy symbol.
Sooo, she's got two holy symbols of Talos now! And they work together!
P.S. I played evil mostly to check out the Edwin Romance mod. I see you have not many info on that. If anyone is interested, let me know, I will post some oppinions about it.