Odd. I checked the pogo_e02 uboot installer pogo_e02.sh, it had the command in it:
$this->bbcode_second_pass_code('', 'ln -s fw_printenv fw_setenv')
from:
http://de3.mirror.archlinuxarm.org/os/armv5te/boot/pogo_e02/pogo_e02.sh
So I assumed it had set it up, and that on pogo e02 it was the same executable as fw_printenv, just with a different command name ...
But I note that the script downloads to /tmp - so probably removed on a reboot. Still from the script you can see how to download fw_printenv ...
Oh yes - note the $this->bbcode_second_pass_code('', 'setenv usb_pgood_delay 10000') is a uboot command - so thats the hassle, you have to execute a uboot command without access to uboot. This you can only do by rewriting the scripts in the uboot variables. So I'd scan the uboot varaibles for the $this->bbcode_second_pass_code('', 'usb start') command, then add the $this->bbcode_second_pass_code('', 'setenv') command to run just before ...
e.g. see the boot commands on my NSA325 which I unrolled here:
https://archlinuxarm.org/forum/viewtopic.php?f=58&t=9798&start=21