TAXI is basically of no use any longer. TAXI is not used, in other words. I could have also used ADSL or DS3. I don't want to dispute the benefit of the small cells on lower link speeds for uncompressed voice etc. Yes, you can compare AAL with MAC layer overhead.
Nobody wants to do that.
You can run IP or other L2 or L3 protocols directly over it without using small cells in between, if you don't use them really. Well I don't think this fair if you put it like this. But actually the real problem area where the cell tax applies is the WAN because there you have to pay for every bit.