Hello Muhammad
Within a single PIM domain, you can have more than one router configured as a mapping agent, however only one router will be active at any time. The following command enables a router as a mapping agent:
ip pim send-rp-discovery loopback 0 scope 10
This specifies the loopback 0 as the source of the mapping agent, and a TTL of 10. The scope essentially determines the maximum distance in number of hops that this router will function as a mapping agent.
Now if there is more than one router configured as a mapping agent within a PIM domain, then each mapping agent makes this announcement independently of the decisions of the other mapping agents.
Concerning BSR, yes you are correct. As Rene states in his Multicast PIM Bootstrap (BSR) lesson:
There can be only one active BSR in the network. BSR routers will listen for messages from other BSR routers, the BSR router with the highest priority will become the active BSR. The highest BSR priority is 255 (the higher the better). When the priority is the same then the router with the highest IP address will become the BSR.
I hope this has been helpful!
Laz