This is a really annoying one. What I ended up using is this:
First, create a group of simple buttons with no data-toggle attribute.
<div id="selector" class="btn-group">
<button type="button" class="btn active">Day</button>
<button type="button" class="btn">Week</button>
<button type="button" class="btn">Month</button>
<button type="button" class="btn">Year</button>
</div>
Next, write an event handler that simulates the radio button effect by 'activating' the clicked one and 'deactivating' all other buttons. (EDIT: Integrated Nick's cleaner version from the comments.)
$('#selector button').click(function() {
$(this).addClass('active').siblings().removeClass('active');
// TODO: insert whatever you want to do with $(this) here
});