This message was posted on behalf of Intel Corporation
What exactly do you mean by sleep mode? Currently the power states of Edison are not available and in fact Bluetooth doesn't need the device to be in a sleep mode to activate sniff mode. BlueZ by default activates sniff mode for devices that must continuously be in contact with the master.
What I mean is, sniff mode can be active when a device is on standby mode but also when it's not. So, you can use sniff mode even if Edison's power states are not available. If you would to check sniff mode configuration you can go to /sys/class/bluetooth/hci0 to check it, however you will have to enable Bluetooth first with the command rfkill unblock bluetooth.