RTOのサイトによると、下記にあてはまれば拒否はできないようです。
"1.5.2 If the rental unit is for sale, when can the property be shown?The landlord must give the tenant written notice at least 24 hours and not more than 30 days in advance. The notice must give the reasons for entering and the time at which the landlord will enter the rental unit, which must be between 8 a.m. and 9 p.m. unless the tenant agrees to another time.
A landlord can give notice setting out a reasonable schedule of viewing times for an upcoming period. The tenant’s rights to reasonable privacy and freedom from unreasonable disturbance must be taken into consideration in establishing a viewing schedule.
See also:
Fact Sheet RTB-125: Selling a Tenanted Residential Property (PDF)Top
1.5.3 Can the landlord show the rental unit when the tenant is not at home?If the landlord complies with the rules given in the answer above, the landlord can show the rental unit when the tenant is not at home." (BC Residential Tenancy)
詳しい事はサイトで調べられます。
http://www.rto.gov.bc.ca/content/rightsResponsibilities/landlord.aspx#152
私も経験があるので、嫌ですよね。
でも、仕方がないので次に住むところを探し始めた方がよいですよ。