Importing a single large table in Azure
It seems there is no way to simply use the .bac files fomr inside the .bacpac archive. 
I had then to revert to bcp to  create a text file that will be the source of another bcp command to create import the dat in the new DB I want.

To export the data and create the file:

bcp "SELECT * FROM $table WHERE someColumn = someValue" queryout "${table}.csv" -U $user -P $password -S $server -d $dbSource -N -k

And then to reimport it as a new table

bcp [$dbTarget].[dbo].[$table] IN "Fresh${table}.csv" -U $user -P $password -S $server -E -N -k