No, it is not always right to say that the expression levels of these variants are similar in different cells. It is important to note that in general, splicing variants of most genes have differential expression in different cell types. Not only the expression levels vary for the different splicing variants, sometime they have differential subcellular localization.
To know more about the expression levels of the splicing variants of Survivin, you can refer to:
1. Previous literature. I think there are some interesting publication dealing with the the splicing variants of this gene.
2. You can have a look at the expression levels of splicing variants by examining your gene of interest in databases that provide information on splicing variants and their expressions. Have a look at this link: http://www.biomedcentral.com/content/supplementary/1471-2105-8-75-s4.doc