I was interested in making pine needle tea myself, and for much the same reasons - historical use, curiosity about survival practices, wanting to try something different. I've done a bit of research myself, before reaching a point where i"m confident enough to try this, and I commend your caution in asking for safety considerations rather than following an article blindly. You have some really good answers already, I especially like Erik's breakdown of species, but I thought I would offer my perspective anyway as a stronger warning and basic approach for those who are interested in this sort of thing.
Since you mentioned the aboriginal people's use of such tea, I would recommend you follow one of their primary safety considerations - know your tree. They knew what was safe, what was dangerous, what was medicinal, at what dosages and which circumstances and what times of year - they spent generations gaining a knowledge of their local plants and their uses, because they had to know in order to survive. What the natives offered the french explorer was specifically "eastern white cedar tea", which was safe and high in vitamin c, not "tea from generic unidentified evergreen" which might be anything.
We have all kinds of information about plants, we don't need local generations to figure this stuff out, if we take the time to look it up. We have identification guides, and all sorts of databases, scientific papers - use them, to find out if the specific tree you have access to, its species, and the use you want it for is safe for you to try before you think about it. Even then, you should proceed cautiously, try a small sample first, and be mindful of any effects on your body before you get into larger or more frequent doses, since even things that are safe might affect different people differently.
So, to get back to the main point - pine tea is from a pine tree, not spruce or fir or larch, not a generic conifer or evergreen. Pine, with long drooping sprays of needles, which are tall trees and not shrubs, with specific types of bark and cones and needles used for identifying the species and cultivar. Most other evergreens are safe, actually, though there are a few you will want to avoid (like yew, look at Erik's through answer for species details) - but the point is, you need to know what your tree is before you even think it might be safe. You should be easily and routinely identifying your trees (at least the relevant ones) to the species and cultivar level before you think to try making a tea from an unfamiliar tree - not just that you "don't think" it is one of the dangerous kind, but that you know what it is, and that it is safe.
Of the pines, I focused on them because it is the name of the tea, and also because only the ponderosa is possibly unsafe - it can be identified by an orange under-coloration to the bark, and a scent like butterscotch, which I can actually remember - and at that, from what I saw it is only a "possibly" - the information I saw says it may be a risk to (especially pregnant) cattle and other ruminents, I saw nothing on the specific dangers humans making tea with this plant... quite possibly because humans will look up its toxicity, see its effects on cattle, and generally not try it to get data on if the dosage in a cupful of tea is safe.
Anyway, the point is that of the pines, I am fairly sure I can recall and identify the one species of pine I would like to avoid, so I might maybe try making tea if I found a pine tree - and I could perhaps recommend someone else try it, with proper precautions anyway - but I would avoid other evergreens (for myself or for recommending to others) because I can't be one thousand percent sure I can recall and identify all of the potentially toxic ones, even though ninety nine percent of them are probably safe.
If you want ceder or spruce or fir tea added to your repertoire, you need to be as familiar with the specific species you want and with the whole group of related trees, to be sure you can identify the right ones and identify (to avoid) any problematic species, all the better to not end up with something dangerous because of an identification mishap. You should not be grabbing random unidentified evergreen unless circumstances are dire.
That's where the ehow article you linked to is actively dangerous, by the way - not only does it not mention identifying your tree (which should be a major emphasis), it shows a picture of what looks like spruce or fir needles (short needles densely populating a branch, instead of the long bunched sprays of pine) along with a picture of pine trees. Even if the spruces and firs are largely safe, conflating the species makes for a really poor approach to identification, and makes it much more likely that someone will grab something evergreen-ish and assume it's probably safe, instead of checking to be very sure.
