You can get your Army pension paid anywhere. You will still receive the annual increases unlike the state pension.
However, like other government pensions, it will continue to be taxed in UK at source and you can't change that.
Reciprocal tax agreements exist between the UK and Canada and any tax you have paid in UK will be offset against tax in Canada and you can't be taxed on the same income twice.
This is covered in the 1978 UK double tax convention between the two countries and last updated in 2015.
However, any pension you receive from UK can be added to any other income earned in Canada to assess the level of tax you pay.
For example, earn 15k pension in UK and taxed in UK so no tax to pay on that in Canada.
Earn 15k in UK and 15k in Canada and your income will be 30k on which the tax level is based but that tax level will only be on the 15k earned in Canada.