RC381 replaces form T2204 and Schedule 8 from tax year 2013 to calculate CPP contribution for both employment and self-employment income.
RC381 is universal for all Canadians. If you have no relation to Quebec, then line 4 of RC381 will be zero. Line 4 is QPP eligible income, if it is zero, no QPP contribution will be calculated. In this case, RC381 will calculate like form T2204/Schedule 8 (as before) in the tax return.
So, don't worry about the existence of form RC381, if you have no Quebec income at all.