It is understandable that you are concerned. There are 13,000 reservists in Ontario that can be deployed any minutes.  In December of 2007 the Ontario Government instituted changed in the Ontario Employment Standards Act that offers job protection for reservist leave or on tour of duty.

Your job is already protected under the ESA if you need to take Pregnancy Leave, Parental Leave, Family Medical Leave, Personal Emergency Leave or Emergency Leave for Declared
Emergencies.  The mentioned leaves have eligibility requirements that you need to take note of. Now added to the list is protection for Military Reservists.  To qualify you need to have worked for 6 consecutive months and you are required to provide reasonable notice, in writing, before beginning and ending the leave, and may be required to provide proof of service if requested by the employer.  Your employer will not have to pay you while you are on leave and is not be required to continue any pension or benefit plan contributions for the duration of your leave. However, if your employer chose to postpone the return date, the employer would be required to make benefit contributions during this additional period of time.  Upon the your return from leave, youre employer is required to reinstate you to the same position if it still exists, or to a comparable position if it does not.