If you're using PowerShell v3, you can do
$url="http://server-name/folder/hosts_in_mm_list.txt"
$reply=Invoke-WebRequest$url
$reply.Content
If you're still on PowerShell v2, you'll have to use the System.Net.WebClient and use for example the DownloadFile method on that object
$url="http://server-name/folder/hosts_in_mm_list.txt"$file="c:\names.txt"
$web=New-ObjectSystem.Net.WebClient
$web.DownloadFile($url,$file)