CSS Transition for only one type of transform?

No! you cannot use transition only for certain value of transform like scale(2).

One possible solution would be as follows: (sorry, you have to use additional html)

HTML

<div class="scale">
<div class="translate">
Hello World
</div>
</div>

CSS

div.scale:hover {
    transform: scale(2);
    transition: transform 0.25s;
}
div.scale:hover div.translate {
    transform: translate(100px,200px);
}