The following NIST standards describe CBC-MAC mentions MAC but give no guidence along these lines. They also mention statistics suggesting that MAC is to guard against random errors, rather than malicious errors.

FIPS 74: Guidelines for Implementing and Using the NBS Data Encryption Standard
FIPS 81: DES Modes of Operation
FIPS 113: Computer Data Authentication

More recently there is current activity for selecting new block modes to accompany the new AES standard. Here are the currently proposed modes.

C.S. Jutla. Encryption modes with almost free message integrity refers to recent consideration of these issues. Jutla mentions that when CBC is combined with MAC-CBC different keys must be used.

This seems to be oral tradition.