I've found the answer to my question:
http://www.cisco.com/en/US/docs/routers/asr1000/configuration/guide/chassis/High_Availability.html#wp1058945
"On the Cisco ASR 1006 Router, the second IOS process can run only on the standby Route Processor. Two IOS processes on the same Router Processor are not possible for any Cisco ASR 1000 Series Router that supports dual RP hardware redundancy configurations since the second Route Processor can support a standby IOS process."