How are you intending to play the push stream? If it's via ASIO, then it will need to be a "decoding channel", ie. using the BASS_STREAM_DECODE flag...
stream=BASS_StreamCreate(freq, chans, BASS_STREAM_DECODE, STREAMPROC_PUSH, NULL);
You can then use BASS_ChannelGetData in your ASIOPROC function to get the data from the push stream.