Given the Mycelium doesn't support BU as far as I can tell... in the event of a hard fork, you'd need to get a BU compatible wallet and import your keys there... all your shiny new BU coins should then show up and you can do with them what you want.
Unless of course the Mycelium team build in BU support in an upcoming update

It is possible to import the addresses in mycelium's first account into electrum, but it doesn't seem possible to import addresses from any other mycelium accounts into electrum. A few people had success with importing the first account in this thread.
https://bitcointalk.org/index.php?topic=1813651.0editIt does work with multiple accounts, a user called Michail1 worked out how to do it.
*snip*
I have tested with a multiple mycelium account wallet.
It will work for other accounts; however, you have to restore them individually. Meaning, follow the process outlined prior for each account within the wallet seed. You get a popup asking which account you want to restore.

My seed has 6 accounts. 0-5 I restored the first 4 as tests to know that it works.