[Cable HSI] How does IPv6 work with Mediacom

I've found some old posts that mediacom doesn't support DHCP-PD (prefix delegation) on IPv6... is this still true? My router requests a prefix for the internal side using prefix delegation, and uses this for IPv6 devices. Is this is supported with Mediacom? CenturyLink does support this, Comcast, Verizon FIOS, almost every major ISP supports this... but does Mediacom??