To check whether a file that has been deployed via a Policy is currently being downloaded by a device, try this command:
if sudo ps aux | grep -v grep | grep lan-cache; then echo "Download in progress." && exit 0; else echo "No download is being performed." && exit 1; fi
If a file is currently being downloaded, the command output will be "Download in progress". If a file is not being downloaded, the output will be "No download is being performed".