AGPS (assisted GPS) is a system that helps GPS devices in getting a FIX situation faster.
In a few words the EPO file contains "hints" that lead the device to find satellites faster.
To use the AGPS feature of your device you have to keep those "hints" updated.
This is useful in poor signal conditions, like when tall buildings or trees make the signal weak.

The new AGPS upload feature is available even in the command line version.
From the usage:
--agps Upload APGS data using the default URL
(or the provided url when available).
--agps-clear Clears the AGPS data in the device
(done before the upload).
--agps-url Specify the URL (file://, ftp://, http://)
to the AGPS (EPO) data.
The basename of this file is usually
Implies agps option.

If you use command line probably you are using it in some sort of BAT script.

This is my experience in mirroring EPO files to get a faster download (and my troubles...)
When uploading EPO files to many devices it could be faster to mirror an EPO file you got somewere, and then upload a local file to avoid a network transfer everytime you send data to the device.
But the EPO file has no checksum informations, so be careful you do not alter the file during the transfer.

Linux example:
cd /home/locale1/agpsdata ; wget -O file.EPO
It works without damaging your file.

Win example:
we call ftp with a script file:
c:\windows\system32\ftp -s:c:\mailtrack_app\ftp.cmd

content of ftp.cmd:
get file.EPO C:\your\path\file.EPO

Notice the "binary" command:
without this the file get corrupted, and you can notice this when - with the GUI - you see the expiration date of the EPO file very far in the future.