Looking at the Transport Canada list of ADs -
here - on the assumption that as state of design, any ADs on the Q series should show up there or have an equivalent to a local AD - shows the following:
The AD which was the reaction to the Scandinavian incidents was CF-2007-20R2. It was last amended in 2009, to add a terminating action as follows:
F. Modification of Main Landing Gear Retract Actuator: - Applicable to DHC-8 Aircraft, Models 400, 401, and 402, Serial Numbers 4001, 4003, 4004, 4006, 4008 through 4182
1. For aircraft main landing gear retract actuators (p/n 46550-7 or 46550-9 or 46550-11) that have accumulated 7,500 or more landings or more than 4 years in service since new at the effective date of this directive:
Within 500 landings or 3 months from the effective date of this directive, whichever occurs first, incorporate Bombardier Modsum 4-901603 to replace the affected retract actuator with a new design retract actuator, p/n 46550-13. Bombardier Service Bulletin (SB) 84-32-55, Revision A, dated 10 March 2008, or later revisions approved by the Chief, Continuing Airworthiness, Transport Canada provides approved instructions for incorporating Modsum 4-901603.
2. For aircraft main landing gear retract actuators (p/n 46550-7 or 46550-9 or 46550-11) that have accumulated less than 7,500 landings, and 4 years or less in service since new at the effective date of this directive:
Prior to reaching 8,000 landings or 51 months in service since new, whichever occurs first, incorporate Bombardier Modsum 4-901603 to replace the affected retract actuator with a new design retract actuator, p/n 46550-13. Bombardier SB 84-32-55, Revision A, dated 10 March 2008, or later revisions approved by the Chief, Continuing Airworthiness, Transport Canada provides approved instructions for incorporating Modsum 4-901603.
3. Incorporation of Modsum 4-901603 provides terminating action to the detailed visual inspection requirements of paragraph C of this directive.
Depending on how old these aircraft are, it is possible that they are coming up on item 2 and are being modified accordingly. Also, the dates for the Australian AD are not necessarily the same as the TCCA one, so it could be even the part 1 requirement, though I'd find that unlikely.
There are a couple of other more recent ADs on the Q400 landing gear which this action could be related to, but there's nothing in the text of those ADs which suggests a link to the previous issue. There is reference to reported incidents, but no details are given (which also suggests not the same incidents, as CF-2007-20R2 is pretty explicit in referring to those, so there'd be no reason to not do so again if apprproaite.)
And while that list of ADs may look long, call up any type with a decent number of aircraft in service and you'll get a fair old list. ADs are part of doing business; frankly, I'd be very wary of an aircraft with a long service history and no or few ADs. Which is more likely: that a design was perfect at entry into service, or that continuing airworthiness is not being properly maintained? I for one am skeptical of claims to perfection.