When I generate a tone in audition at 0dB (or any other lever)and bring it into a multitrack track, the level is always 3dB lower. If I double click the same file in the mutitrack to view it in the Waveform the level is as expected.
By default, the Multitrack signal chain adopts a -3dB dip in the center of a stereo mix due to Pan Law. You can find out more about Pan Law at http://en.wikipedia.org/wiki/Pan_law but in essence, it ensures a consistent level as a signal pans from left-to-right, or vice versa. Otherwise, when a signal is panned toward the center, it will grow louder.
You can disable this behavior by opening Preferences > Multitrack and changing the "Panning Mode" preference to Left/Right Cut (Logarithmic) or adjust the level as desired.