Can spin-1/2 emerge as a property of quasiparticles if original description of the system was without spin?

The answer is Yes. See

A physical understanding of fractionalization

http://arxiv.org/abs/hep-th/0302201 Quantum order from string-net condensations and origin of light and massless fermions, Xiao-Gang Wen; Spin-1/2 and Fermi statistics from qubits

http://arxiv.org/abs/hep-th/0507118 Quantum ether: photons and electrons from a rotor model, Michael Levin, Xiao-Gang Wen; Spin-1/2 Fermi statistics from rotors

In fact, every lattice QCD or lattice QED is a model where spin-1/2 emerge from something with no spin. But in lattice QCD or lattice QED, Fermi statistics is added by hand.

Not only spin-1/2, almost everything can emerge from interacting qubits. Wheeler's "it from bit" represents a deep desire to unify matter and information. In fact, it happend before at a small scale. We introduced electric field to informationally (or pictorially) describe Coulomb law. At this stage, the electric field is just information (bit). But later, electric field became real matter with energy and momentum, and even a particle associated with it.

However, in our world, "it" are very complicated. (1) Most "it" are fermions, while "bit" are bosonic. Can fermionic "it" come from bosonic "bit"? (2) Most "it" also carry spin-1/2. Can spin-1/2 arises from "bit"? (3) All "it" interact via a spectial kind of interaction -- gauge interaction. Can "bit" produce gauge interaction? Can "bit" produce waves that satisfy Maxwell equation? Can "bit" produce photon?

More generally, there are Eight wonders in our universe (ie "it" has eight wonders)::

1. Identical particles.
2. Gauge interactions.
3. Fermi statistics
4. spin-1/2
5. Chiral fermions.
6. Small mass of fermions. (Much less than Planck mass)
7. Lorentz invariance.
8. Gravity.

It turns out that we can only produce the first of eight wonders from bits.

However, if we start with qubits, we can obtain Fermi statistics, spin-1/2, Maxwell equation, Yang-Mills equation, and the corresponding gauge interations. So far, we can unify seven out of eight wonders (1 -- 7) by qubits, and we are trying to add the gravity (see http://arxiv.org/abs/0907.1203 ).

So It from qubit, not bit. Bit is too classical to produce Gauge interactions, Fermi statistics, and Chiral fermions. Those phenomena (or properties) come from quantum many-body entanglement, which exists only for qubits. (See also What is the relationship between string net theory and string / M-theory? )