I can understand why the NDP's response to the Cons' lobbying deflection was to demand more rather than criticizing the idea altogether: as laughable as it should be for the most secretive government in recent memory to keep pretending to have any interest in transparency, they might well be able to score political points with their base by bleating that the opposition parties don't want to face their definition of accountability. But it's worth taking a step back to ask whether there's actually any point to requiring registration of dealings with opposition MPs other than to make life more difficult for anybody opposed to the government.
After all, the main purpose of restricting lobbying activities would seem to be to make sure that decision-makers aren't influenced by unknown outside forces when making policy choices which can't be easily reviewed or debated. Which means that the obvious focus would seem to be the cabinet ministers who have the formal authority to make independent decisions which directly affect the interests of Canadians, along with high-ranking officials and partymates who wield disproportionate influence.
Needless to say, that need for transparency goes doubly in a political culture where statutes tend to serve mostly to set out authority which can be exercised by the executive in any number of directions - meaning that the effect of federal action on any particular person is almost entirely driven by discretionary choices where lobbying a single minister can make all the difference.
In contrast, no single backbench member of Parliament has the slightest ability to set policy independently or secretly: the main forms of influence for MPs are through fully-documented participation in Parliamentary debates and votes. And indeed under the Cons, even the will of Parliament as a whole (whether in the form of binding orders or legislation) is routinely flouted - again at the whim of the executive branch which is looking to deflect attention from itself.
As a result, it doesn't make much sense to me to suggest that efforts to raise issues with backbench MPs or opposition parties should be layered with the same type of restrictions that might be appropriate when an interest group seeks to influence government decision-makers directly outside the channels of public debate.
What's more, the application of lobbying rules only figures to make it more difficult for groups who are already on the wrong end of the Harper Cons' brand of government by grudge to voice their concerns to the parties best positioned to raise questions about the executive vindictiveness. And it will also allow every real concern about government decisions being influenced by outside actors to be met with trumped-up finger-pointing toward the opposition - making it far more difficult for genuine concerns to receive the focus they deserve.
In sum, while there's plenty of reason for the opposition parties to be wary of the politics of rejecting greater perceived transparency, we shouldn't ignore the question of whether the move actually makes sense in substance. And if the end result is that greater restrictions on the opposition parties will ultimately serve only to better cloud what the government is doing, then it's worth fighting back rather than simply accepting the Cons dictating who the opposition can and can't meet with as the price of avoiding conflict.