I have my own reader. After a lot of research, I found an off-the-shelf reader in the tolling/parking industry that is able to read ISO 10374 formatted tags, which the standard that AEI is based on. I had to write my own software to convert the raw tag data (128 sting) to readable information, based on the ARR S918, which is the AEI standard.
The big challenge is getting close enough to the tracks to read the tags without trespassing. I found that I can get reliable data at about 20' from the rail, running 2 W into a 13 dBi horizonally polarized antenna for a total of 23 W ERP.
I logged date for about a month, and correlated it with noise data (I'm a noise control engineer), as part of a feasibility study on using AEI for rail noise studies. It worked quite well. I can determine the consist, direction, length, and speed of the train from the tag data.