def METHOD_NAME(networks, topo_id):
    """
    Returns the subnets of all remote ASes the SIG in topo_id is connected to.
    :param networks dict: Scion elem to subnet/IP map.
    :param topo_id: A key of a topo dict generated by TopoGenerator.
    :return: String of comma separated subnets.
    """
    rem_nets = []
    for key in networks:
        if 'sig' in key and topo_id.file_fmt() not in key:
            rem_nets.append(str(networks[key][0]['net']))
    return ','.join(rem_nets)