Because here http://www.amxmodx.org/doc/index.htm...Fread_file.htm does not specify this matter i think that it is possible.You could try this by writing a little script for test to check if file C:\lol.txt exists.If it exists in this test plugin you could try to read from it and log it(to see it in console).Don't forget to add "debug"(without quotes) in plugins.ini after this test plugin.
I hope you understand my idea.As soon as I can I'll do this test on my own.