Are USAR SM, who are ordered to active duty for Operational Support, authorized the Army Reserve Components Overseas Training Ribbon?

Overseas can include Canada. As long as you do 10 days in a foreign country you qualify. Travel time does not count.

According to AR 600-8-22 Section 5-3, it states:
5–3. Army Reserve Components Overseas Training Ribbon
a. The ARCOTR was established by the SECARMY on 11 July 1984 as announced in DAGO 1990–15. It is awarded to members of the RC of the Army (ARNG and USAR), for successful completion of annual training or ADT for a period not less than 10 consecutive duty days on foreign soil. All ARNG and USAR Soldiers who accompany the RC unit (including unit cells) to which they are assigned or attached as active duty for operational support during overseas training are also eligible for the award. Effective 11 July 1984, all members of the ARNG and USAR are eligible for this award if they were active Reserve status members of the ARNG, USAR (not on active duty in the Active Army), or AGR Soldiers at the time their unit underwent annual training or ADT on foreign soil.

Short answer yes

I am 90% sure that ADOS missions do not qualify. The ARCOTR is typically awarded for units or members of units that do at least 10 consecutive days of ADT overseas.

You may qualify for the standard Army Overseas Training Ribbon with ADOS, though. I am not very clear about that, though

I believe that you are eligible for the Overseas Service Ribbon not the training ribbon. If you were on AT and CDC went to Germany you would be there in a training capacity. Since you are there in an active capacity the other award applies. At least that's what I was told.

I would say contact the personnel office who is handling your call back notification

Always a good idea to have anything dress uniform in extras for inspection purposes anyway