Do you mean smth like this?
```
<div id="contact-carrier" class="carrier-wrapper">
  <span class="phone-type"></span>
  <span class="phone-type-separator" data-l10n-id="thread-separator"></div>
  <span class="phone-details"></span>
</div>
```
```
var carrierTag = document.getElementById('contact-carrier'),
    phoneType = carrierTag.querySelector('.phone-type'),
    phoneDetails = carrierTag.querySelector('.phone-details');

phoneType.dataset.l10nId = "type";
phoneType.textContent = "type"; // Probably we need this line if "type" isn't declared in locale file
phoneDetails.textContent = "details"

navigator.mozL10n.translate(carrierTag);
```

It it's ok for you, I can get rid of template then.