Correction:

>> I know AppliedMicro have been using and ARM bus for some time.

> Really? As far as I know they've been using IBM's CoreConnect PLB
> in their Power Architecture chips, not ARM's AMBA.

Sorry, I was wrong. Actually, they've been using a combination of PLB and AMBA (AHB, APB) in their chips, with bridges in between.

http://www.acaltechnology.com/_files/franchise/AppliedMicro/catalogues/Acal_BFi_AppliedMicro_Shortform_(LowRes).pdf
http://www.acaltechnology.com/_files/franchise/AppliedMicro/datasheets/APM86290_PB_20110103_v1_05.pdf
http://images.anandtech.com/doci/5326/CatalinaAPM86491.png

According to the first one of those PDF files, the PPC460EX seems to have been Applied Micro's first chip to implement AMBA buses.