just make sure you connect the 2nd BTID to the primary ID you need to create new IDs for anyone who uses smarttalk
have you tried it yet? does it not ask for an account number which would then tie the 2 IDs together to one account
See this link about BTIDs
Why do you want 2 BTIDs. The only reason to have more than one is if you have an email sub account that you want to "gift" to somebody or have as a stand alone email account in which case you could set up a BTID for that email.
See link and the sub links at the foot of the page
If have two BTID's you would not be charged for them.