Yes, that's why you may may want to work with your mobile device manager or your network admin to make sure that you get a certificate from a vendor who is part of the trusted CA's list on almost all mobile devices. Normally these are companies like GoDaddy, Verisign, RSA Incommon etc etc.,
However, some companies have their own cert authorities / certs that they push out to the mobile devices. So, maybe getting certs from such internal vendors is preferred in such cases. That's why its better to work with your network admins to sort it out
_R