Yes they did:
Dozens of technology companies, industry trade groups, and encryption experts have been submitting documents to support Apple, all
catalogued on Apple's website.
AT&T, Intel, and the Electronic Frontier Foundation filed separate amicus briefs this morning, as did the Consumer Technology Association in partnership with the Business Software Alliance [
PDF], a group that includes
Microsoft, Salesforce, Oracle, IBM, and Autodesk.
More amicus briefs are expected to be filed throughout the day, including one from a consortium that includes
Google, Nest Labs, Facebook, WhatsApp, Evernote, Snapchat, and Mozilla.