IE11 supports the transform attribute in SVG even though it doesn't recognize the CSS style.
Fortunately, you can simply set the attribute to match the style using JavaScript:
var g = document.querySelector('.st8'),
transform = getComputedStyle(g).getPropertyValue('transform');
g.setAttribute('transform', transform);
.st8 {
-ms-transform: rotate(45deg); /* doesn't work on IE */
transform: rotate(45deg);
}