Use similar breakpoints to new WDN grid variables. Streamline so dependency is only on the set variable.

unl_mq.less

/*
*
* !DO NOT EDIT THE CSS FILES, THEY ARE BUILT WITH THE LESS CSS!
* less/dir/file.less
*
* ---------------------------
* Styles associated with the XYZ
* ---------------------------
*/
@import "../_mixins/all.less";

// Breakpoint rules (follows WDN gridv3)
@bp1: ~"min-width: 480px";
@bp2: ~"min-width: 768px";
@bp3: ~"min-width: 960px";
@bp4: ~"min-width: 1040px";

// Add all base (screen width doesn't matter) here


// For all the media queries

// 480px wide
.bp1() {

}

// 768px wide
.bp2() {

}

// 960px wide
.bp3() {

}

// 1040px wide
.bp4() {

}

// This is what's outputed in the media queries
@media only screen and (@bp1) {
    .bp1();
}
@media only screen and (@bp2) {
    .bp2();
}
@media only screen and (@bp3) {
    .bp3();
}
@media only screen and (@bp4) {
    .bp4();
}

// Output the media queries without the media queries for IE7 & IE8
ie7, .ie8 {
    .bp1();
    .bp2();
    .bp3();
    .bp4();
}

Base for the LESS files in the UNL WDN Templates project.