Hi micschroth,
Thanks for your message.
A current iPad device equipped with 128 GB will be perfect to run Cubasis, LTE is not required to run the app.
Cubasis projects can be imported with Cubase via the available Cubasis project importer extension.
Cubasis also allows to import audio and MIDI files, but does not provide a dedicate Cubase project file import function.
Here is a short tutorial that explains the process how to import Cubasis projects into Cubase: http://musicappblog.com/cubasis-workshop-2/
Below please find a few links to learn more about Cubasis.
Cubasis 2 website
Cubasis - Official tutorials & teasers
We hope to welcome you as a Cubasis user soon!
Best,
Lars