My brother did a Bachelor of Science degree, Psychology Major, at the University of Manitoba.
I am curious if it is common for Psychology to be offered through Science and Arts faculties as opposed to just Arts. Do most Universities offer this?
In the US, Psychology is rarely considered part of the arts, and is generally called a "social science", with most degrees being offered as "bachelor's of science". Oddly, psychology is often excluded from "STEM" designations, where it is often not considered under the umbrella of either "science" or "technology". For more info on this, see the American Psychological Association's article on Psychology as a Core Science.
Regardless, at least in the US, Psychology is generally not classified as an art. It's a field in kind of a weird place, classification-wise. There often is some flexibility in degree classification here, as many Universities allow you to get a "bachelor or science" (BS) or "bachelor of arts" (BA) in nearly any field (even something like Physics or Math). The BS vs BA classification often is just a question of what other classes you take, such as in language (BA's usually require foreign languages and more classes in humanities). Just in case things aren't quite confusing enough for you.
Psychology's position as "social science" is something in-between the humanities and science-proper, with some areas clearly being heavily related to the arts (such as dance psychology), while some are actually housed within engineering schools (human factors, psychology of engineering, etc). Still other fields - or descendants - of psychology are hosted in schools of technology like computer science (human computer interaction, for instance). So the field of psychology, perhaps more than most fields, tends to defy easy classification and every institution has their own unique interpretations and departmental history.