The following functionality allows you to receive email notifications for subscription events.

While on your store admin's Manage Product Categories, enable send admin email in the Email Options, input the email addresses you want to be notified in admin email(s), and then set an admin email subject.

At this snippet in the admin text email template if you want to be notified whenever a customer registers a new subscription.

{% if is_new_subscription %}
{# INSERT CUSTOM CODE HERE #}
{% endif %}

In case you want to modify the email subject to be more descriptive to the newly-created subscription event, add this snippet below the above snippet:

{% if is_new_subscription %}
{% set custom_subject = 'New Subscription by ' ~ billing_address.first_name ~ ' ' ~ billing_address.last_name ~ ' [' ~ order_id ~ ']' %}
{{ custom_subject|fc_output_data('email_subject') }}
{% endif %}

If you don't want to send email receipts for subscription renewals, but just for initial subscription orders, subscription cancels and subscription updates, you can do that with a setting on your store's advanced settings page. Look for the “send emails for automated subscription renewals” checkbox and uncheck that to stop email receipts being sent for subscription renewals. More details on the subscriptions wiki page.

If you need to handle it conditionally within your templates though, you can add the following code below the above snippet:

{% if has_subscriptions and not is_new_subscription %}
{% set custom_subject = '' %}
{{ custom_subject|fc_output_data('email_subject') }}
{% endif %}

At this snippet in the admin text email template if you want to be notified whenever a customer cancels a subscription.

{% if is_subscription_cancel %}
{# INSERT CUSTOM CODE HERE #}
{% endif %}

As with the above optional snippet, you can include this in the custom code section of the cancelled subscription condition:

{% set custom_subject = 'Cancelled Subscription by ' ~ billing_address.first_name ~ ' ' ~ billing_address.last_name ~ ' [' ~ order_id ~ ']' %}
{{ custom_subject|fc_output_data('email_subject') }}

At this snippet in the admin text email template if you want to be notified whenever a customer modifies a subscription.

{% if is_subscription_modification %}
{# INSERT CUSTOM CODE HERE #}
{% endif %}

You could also change the email subject as you would with the newly-added and cancelled.

Feel free to combine the conditions in one conditional statement separated by an and statement.