you can probably avoid additional resources used by power-shell by simply mapping the drive on the destination server through tsql and restore the backup, you do not even need to copy file

exec xp_cmdshell "net use x: \\sourceserver\backupdir /user:domain\user password"
go
restore database demodb from disk='x:\demodb.bak'
go
exec xp_cmdshell "net use x: /delete"
go