Not according to the configuration guide:
http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst6500/ios/15-1SY/config_guide/sup2T/15_1_sy_swcg_2T/instant_access.pdf
From page 2:
IA client ports do not support these features:
* Configuring EtherChannels with combination of FEX Ports from different FEX-IDs or
combination of FEX ports with IA parent switch linecard ports is not supported.
* FEX host port EtherChannel load balancing is not supported.