We found out recently that some estimates show the costs of the bipole III power line increasing by $2b. This increase is on the converter half of the equation (now three quarters I suppose) as opposed to the power line part. In the article, Mary Agnes Welch states:
The converter stations are needed whether the line runs down the west side, as the NDP government has mandated, or through the boreal forest on the east side of Lake Winnipeg.
Unfortunately, due to it's length, its characteristics make it unsuitable to operate with either of the existing Bipole I or II converters, requiring it to have its own converters designed to operate with the longer line.
When we originally looked at the proposal to build the line down the east side, it was at that point being tied in to the existing conversion equipment, and at that point, it was–the converter stations, without considering new generation being added to the system or the reliability associated with something happening to the existing converter stations, it was not included at that point.