Before the introduction of the "HSRP Support for MPLS VPNs" feature, HSRP used to add the ARP entries and IP hash table entries to the default routing table instance, even if the interface was part of a VRF. This was causing ARP and ICMP echo requests for the HSRP virtual IP address to fail. With this feature, the entries are added to the IP routing table belonging to the VRF.
This feature enables the use of HSRP for providing PE router redundancy when connected over a LAN. The PE routers can be configured to track their connections to the rest of the network and have their HSRP priorities adjusted to assume the active or standby role, depending on whether they have a route to the destination.