Can you use BigQuery to run on top of Bigtable
Yes you can. Link to Bigtable using it as an external table. It is not then created in BigQuery itself. Per the documentation:


  To query Cloud Bigtable data using a permanent external table, you:
  
  
  Create a table definition file (for the CLI or API)
  Create a table in BigQuery linked to the external data source
  Query the data using the permanent table
  


It is in Beta, but this is standard for Google and usually only lasts 6 months or so. In my experience the features and products and alot more stable in Beta than you find on other providers.