It probably does not (yet) have the generated client for cloud bigtable checked in (but I'm sure it will), but you can always use it to generate a client. You pass it the API to use on the command line, it will go fetch the docs it needs to make your client, and put its source where you tell it to.
This uses the HBase API. You just connect to it like you would any other HBase cluster, using an HBase client. It's not like e.g., BigQuery or Datastore where you need the API client. You include a JAR and then connect to HBase like normal.
The website claims that you must use their customized version of the Java HBase client library: it does not claim it is network compatible, and seems to state it is API compatible with the Java API (but then describes numerous subtle differences).
> To access Cloud Bigtable, you use a customized version of the Apache HBase 1.0.1 Java client.
