Yes it is possible. If you test sample cells are proliferating more than the control or are metabolizing MTT more than the control. One important point to keep in mind is that the absorbance reading should not be saturated (i.e., its intensity should not increase beyond a certain point as after that you will not be able to detect any difference between different groups. Therefore you will not detect a difference even if your test cell group is proliferation more than the control (or vice versa). This will have to optimized according to your cell type and instrument that you use for recording absorbance.
Yes, In case of cellular proliferation we can get higher percentage of cellular viability using calculation of ratio between treated cell and non-treated/standard cell OD values in percentage.