Virtual MAC address: MAC address is generated automatically by HSRP. The first 24 bits will be default CISCO address (i.e. 0000.0c). The next 16 bits areHSRP ID(i.e. 07.ac). The next 8 bits will be the group number in hexadecimal. e.g- if the group number is 10 then the last 8 bits will be 0a.
I am not sure that I 100 percent understand your question. But based on what I think I understand here is my response: I think we are talking about the arp table and not some other type of mapping or table content. If R1 would send a gratuitous arp for the HSRP virtual address it would not use the mac 0123.4567.89ab but would use the multicast mac associated with the particular HSRP group configured on the interface. So R2 would have an arp entry for 172.16.0.1 with the physical mac address and have an arp entry for 172.16.0.5 with the virtual mac address.