I recently wrote a quick little fabric function to create a fabric shell. This works with a stock fabric install, you just might have to change where you import it from. It is at my Github page below.

https://github.com/mzupan/fabric_shell

If you place shell.py in the same directory as fabfile.py you can use it like

from fabric.api import *
from fabric.decorators import hosts

import shell

env.hosts = [
    'host1.domain.com',
    'host2.domain.com'
]

@hosts('')
def cmd():
    shell.shell()

Then you can use like like

$ fab cmd
[] Executing task 'cmd'
fabric::> id
[host1.domain.com] run: id
[host1.domain.com] out: uid=1020(mzupan) gid=1020(mzupan) groups=1020(mzupan)
[host1.domain.com] out: 
[host2.domain.com] run: id
[host2.domain.com] out: uid=1020(mzupan) gid=1020(mzupan) groups=1020(mzupan)
[host2.domain.com] out: 
fabric::> .sudo id
[host1.domain.com] sudo:  id
[host1.domain.com] out: uid=0(root) gid=0(root) groups=0(root)
[host1.domain.com] out: 
[host2.domain.com] sudo:  id
[host2.domain.com] out: uid=0(root) gid=0(root) groups=0(root)
[host2.domain.com] out: 
fabric::> 

Right now any command that is issued in the fabric shell gets run on all hosts in env.hosts and if you add .sudo in front of the command it will run them as root.