It is possible to access the Google Play Developer API using Service Account flow.  
Official sample shows how to authorize with Service Account using service account email and p12 file.
The relevant credential creating code looks as following:  
private static Credential authorizeWithServiceAccount(String serviceAccountEmail)
        throws GeneralSecurityException, IOException {
    log.info(String.format("Authorizing using Service Account: %s", serviceAccountEmail));
    // Build service account credential.
    GoogleCredential credential = new GoogleCredential.Builder()
            .setTransport(HTTP_TRANSPORT)
            .setJsonFactory(JSON_FACTORY)
            .setServiceAccountId(serviceAccountEmail)
            .setServiceAccountScopes(
                    Collections.singleton(AndroidPublisherScopes.ANDROIDPUBLISHER))
            .setServiceAccountPrivateKeyFromP12File(new File(SRC_RESOURCES_KEY_P12))
            .build();
    return credential;
}
Folks at AzimoLabs wrote a post where they retrieving store reviews using this method. They also open-sourced their tool.  
You can also authorize with Service Account using JSON key type:  
private static Credential authorizeWithServiceAccount() throws IOException {
    log.info("Authorizing using Service Account");
    try (FileInputStream fileInputStream = new FileInputStream(JSON_PATH)) {
        return GoogleCredential.fromStream(fileInputStream, HTTP_TRANSPORT, JSON_FACTORY)
                .createScoped(Collections.singleton(AndroidPublisherScopes.ANDROIDPUBLISHER));
    }
}
More detailed instructions can be found here.