Cisco Systems XR manual Which specifies that TACACS+ authorization is used, SR-11

Authentication, Authorization, and Accounting Commands on Cisco IOS XR Software

aaa authorization

Examples	The following example shows how to define the network authorization method list named listname1,
	which specifies that TACACS+ authorization is used:
	RP/0/RP0/CPU0:router# configure
	RP/0/RP0/CPU0:router(config)# aaa authorization commands listname1 group tacacs+
Related Commands	Command	Description
	aaa accounting	Creates a method list for accounting.

Cisco IOS XR System Security Command Reference

SR-11