Are pathcopyfrom and pathcopy2 absolute or relative paths? If relative, are you sure you know what directory you're starting in? In cPanel cron, it's normally /home/ACCOUNTNAME, but I don't know if it's different in LPCP cron. Generally it's safest to assume nothing about the path, and use absolute paths (starting with / ).
You should print (echo) the error message that the target file already exists. It will show up in the email sent by cron. Speaking of which, why are you bothering to send an email? The cron job should send you an email that includes anything written to stdout or stderr. It looks like this project was adapted from a browser-run script.
Try taking the '@' off the fopen() call. Maybe there's an error message that you'd like to see.
As a matter of style, I would suggest putting the two paths, and the filename, in three variables. Then you glue the appropriate path and the filename together when used. Is "pathcopyfrom" actually a URL rather than a directory path? There might be security restrictions going on (e.g., fopen barred from opening by URL) that stop you from opening a URL. If this is a directory-to-directory copy, using exec("cp ". $from . " " . $to); might be easier, but be sure to check if the target file already exists (it will be overwritten if you go ahead with the copy).
As for the path given in the Wiki, if they say /usr/bin/php5/bin/php for example, your cron command line would be /usr/bin/php5/bin/php -q /home/USER/public_html/PATH/copy_email.php. I don't see anything in your code that shouldn't work with PHP 4, so it's probably a moot point. Without the -q flag, you're probably seeing a line or two of "header" stuff (e.g., "text/html") in your email.