The question was this:
"Is a reader able to interpret from the above that a NON gps 406 ELT like an AK 451 may be installed by the builder in Canada?"
So I think I answered that correctly ... You absolutely can install a non-GPS aware ELT 406 unit.
As to who can do it, the exemption letter can be found here:
http://www.tc.gc.ca/CivilAviation/Regserv/Affairs/exemptions/docs/en/2052.htm
This letter allows AMEs, and non-avionics AMOs to work on TSO C126 ELTs, given certain conditions, one of them being like you said that the unit must not interface with other systems.
Says nothing about owners though.
For owners, the regular 571.04 reg always applies anyways:
http://laws-lois.justice.gc.ca/eng/regulations/SOR-96-433/FullText.html#s-571.04
"571.04 No person shall perform the specialized maintenance set out in Schedule II to this Subpart on an aeronautical product
other than an aircraft operated under a special certificate of airworthiness in the owner-maintenance or amateur-built classification, except in accordance with ..."
Where Schedule II is full of goodies, and includes many many things that home-builders do all the time (Like working on your wings, or engine mount, or installing a full EFIS suite, etc.), and said home builders are exempt from that rule at all times anyways (You wwouldn't get very far if you didn't, as it's pretty broad ranging).
So it seems that amateur builders can not only install and certify their C126 installation, they can do so even if the ELT interfaces with other systems, since that restriction only applies to those specially exempt from 571.04 by that letter, which isn't you guys (I won't say "us" since I'm not building yet!
), because you always are.
Found you a rule that gives you MORE freedom that you thought you had, how about that