This thread is about Bluetooth HomeKit devices, and in particular the Elgato Eve ones. AIUI the Ecebobee products are IP based so this is a bit off topic here?
Events are especially important for BLE devices as they are more likely to be battery powered and we don’t want to wake the device up once a minute to poll if we can help it.
I cannot say how particular devices will behave when we have event support in homekit_controller, a lot of it is up to the devices themselves. The current implementation will subscribe to events for any characteristic that it polls if the device supports it. So if your temperature sensor supported events then Home Assistant would be able to make use of them. For the temperature characteristic, this is optional for the accessory manufacturer though.
It’s likely that polling will still be used in addition to events at first. We don’t know how reliable the new event code is, so we’ll keep the existing code in place while we see. Even if we relax this and poll event characteristics less often, we’ll of course still be polling characteristics that don’t support events.
Regarding the resolution of data collected - we support whatever the underlying device supports, and if the device reports a change we report the change to the HA state machine.