I found some sources that described Latin as having "dark l" or "intermediate l" after consonants (in contrast with "light l" in the geminate /ll/ or before /i/), but they seemed to be based on early evidence, like the epenthetic /u/ that developed before /l/ in words like stabulum. I don't know of any evidence that Proto-Romance had dark l after consonants. Do any Romance languages have developments like Cl > Cw?
As Nort says, it seems simpler to suppose that /j/ is a development from /ʎ/, since this kind of de-lateralization is well-attested as a sound change in the relevant areas, and as linguoboy says some languages in Spain show Cl > ʎ or lC > jC.
[kt]

[xt]

[çt]

[jt] looks basically plausible and, as other people have said, usual, although I'm not sure if there is any real certainty about the order of fronting vs. voicing/lenition. According to Wikipedia, in Modern Spanish, words like "obtener" and "optimista" may be pronounced with [βt], with a voiced lenited sound preceding the following stop. Considering that voicing and lenition of Latin singleton /k/ > [ɣ] is also attested intervocalically, it also seems plausible to me to suppose something like [kt]

[xt]

[ɣt]

[jt].