Howdy Ken!
The following code would remove the default iCal feed generator from running:
remove_action( 'tribe_tec_template_chooser', array('TribeiCal', 'do_ical_template' ) );
From there you could add your own action that duplicates the functionality of do_ical_template() and more importantly generate_ical_feed(). Of course some modifications to those functions would be necessary if your duplicate them, as they are currently within the TribeiCal Class. Once you have the function duplicated and working, then I would change the header() call within your custom generate_ical_feed() which specifies the default filename.
I wish it was easier. I think this could be a good area for a feature recommendation. For instance, instead of saying iCal-Tribe it could use your blogname instead. If you do have any feature recommendations like this please put them up on our uservoice page: https://tribe.uservoice.com/forums/195723-feature-ideas
Does that help? Thanks for posting!
– Brook