Discovery is entirely dependent on the target responding to one of the below probes.
If the your targets will respond to those probes while in sleep or hibernate mode then they will be discovered.
In addition to what Jeffrey said -- MVM, or any device for that matter, will not detect a computer in Hibernation on the network. Hibernate offloads the content of the computer's memory and saves it to the hard drive and then shuts down, so for all intents and purposes it's powered off. I'm about 80% sure the same is true with Standby. The main difference between Standby and Hibernate is that Standby maintains power to the memory, but I don't think it keeps much more than that powered. All non-essentials are powered down in this state so I would assume this means the network card is also offline, but the easiest way to verify would be to put a computer into standby and then look at the lights on the NIC -- if they are lit up you may be in business, if not they're not.