It seems that having Creative Cloud through an ETLA only provides access to the CC set of software but not all the services that are provided by Creative Cloud "Membership".
For instance, it doesn't look like you get:
Online storage is "Customized" per account as opposed to 20GB for Individual and 100GB for Team (http://www.adobe.com/products/creativecloud/buying-guide-at-a-glance.h tml)
And "services" are also a custom solution that is negotiated between your company and the Adobe account rep.
The "services" are the bit that would make Ligthroom Mobile work correctly, I believe.
I'm in the same boat, by the way. When I log into the Creative Cloud website, it shows that I have the free plan eventhough the company I work for has an ETLA for Creative Cloud. We just have access to the software, not the services provided in a different type of Creative Cloud membership.