I won't comment on Clark or the politics behind it all as even if none of this were going on, she is a lame duck on the road flapping her wings in panic. However, it is my belief that as this is an interprovincial pipeline it falls under federal juristiction via the National Energy Board and they will need to find other ways to shoot it down rather than just saying "we aren't signing on".
http://www.neb-one.gc.ca/clf-nsi/rthnb/whwrndrgvrnnc/rrspnsblt-eng.html
http://www.neb-one.gc.ca/clf-nsi/rthnb/whwrndrgvrnnc/pplnpwrlnndtknw-eng.html