* March WCS quoted at $25.75/bbl under WTI * Narrowest WCS spread since Oct 23 * March synthetic $0.75/bbl over WTI CALGARY, Alberta, Feb 7 (Reuters) - Canadian heavy crude prices rose again on Thursday, hitting a 15-week high in a rally fueled by reduced pipeline rationing and talk of some players getting caught short. Western Canada Select heavy blend for March delivery last sold for $25.75 a barrel under benchmark West Texas Intermediate, narrowing its discount from a Wednesday settlement of $26 a barrel under, according to Shorcan Energy Brokers. That was its slimmest differential since Oct 23. Traders have expressed surprise at this month's steady gains after two months of discounts that at times topped $40 a barrel. Surging production, tight pipeline capacity and a series of refinery outages were blamed for the slump, and those fundamentals are largely unchanged. However, apportionment levels on Enbridge Inc's pipeline network to the U.S. Midwest are below those set for last month, easing some of the price pressure, traders have said. In addition, the start-up of Imperial's 110,000 barrel a day Kearl project in northern Alberta, first expected to begin commercial production at the end of 2012, is now targeted for the end of the first quarter. Full production is scheduled for the "next several months". Light synthetic crude prices also strengthened. It was last quoted at 75 cents above WTI, compared with 60 cents above on Wednesday. This week, Suncor Energy Inc and Syncrude Canada reported lower oil sands-derived crude production for January.