FOP2 does not care about virtual things, it monitor devices, what is your button.cfg file in one of those cases you mention? What you cannot do is monitor the same device twice, having for example
[SIP/100]
type=extension
extension=100
label=something
[SIP/100]
type=extension
extension=101
label=another
The above won't work well, status for SIP/100 will be reflected on one of the buttons only.
